December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

FEATURES

High level of integration to allow assembly in intelligent
battery packs

Accurate charge and discharge account

Large dynamic range of charge and discharge currents

Independent settings of charge and discharge efficiency

2 V minimum supply voltage (2 cell operation)

Temperature protection of batteries during charging

Temperature controlled self-discharge

Accurate charge current regulation

Two charge amount display modes, LCD and LED.

GENERAL DESCRIPTION

The SAA1501T is intended to be used as a battery monitor
and charge current control circuit in rechargeable battery
systems.

The SAA1501T is processed in BiCMOS technology
where the benefits of mixed bipolar and CMOS technology
is fully utilized to achieve high accuracy measurements
and digital signal processing in the same device. The
general function of the integrated circuit is a Coulomb
counter. During battery charging, the charge current and
charge time are registered in a Coulomb counter. During
discharge, the discharge current and time are recorded.
The momentary charge amount of the batteries can be
displayed either on an LCD screen or on an LED bargraph.
Using the SAA1501T, intelligent batteries or intelligent
battery powered systems can be easily designed with only
a few external components.

QUICK REFERENCE DATA

ORDERING INFORMATION

SYMBOL

PARAMETER

CONDITIONS

MIN.

TYP.

MAX.

UNIT

supply voltage

2.0

3.0

4.3

supply current

= 3 V;

= I

= 60

1.2

1.7

CCstb

supply current in standby mode

= 3 V;

CSI

= V

DSI

= 0 V

100

osc

fixed oscillator frequency

osc

= 820 pF;

ref

= 51.5 k

4.2

kHz

i(s)

input sense voltage (pins 9 and 10)

1.6 V

amb

operating ambient temperature

+70

TYPE NUMBER

PACKAGE

NAME

DESCRIPTION

VERSION

SAA1501T

SO24

plastic small outline package; 24 leads; body width 7.5 mm

SOT137-1

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

PINNING

SYMBOL

PIN

DESCRIPTION

supply voltage

enable output

duty cycle capacitor output

charge counter capacitor output

maximum average charge current
setting input

ref

current reference resistor input

DCC

discharge current conversion resistor
input

CCC

charge current conversion resistor
input

CSI

charge sense input

DSI

discharge sense input

TEMP1

temperature sensing resistor 1 input

TEMP2

temperature sensing resistor 2 input

osc

oscillator capacitor input

BUZ

buzzer output

FULL

battery full indication output

L100

100% segment indication output

L80

80% segment indication output

L60

60% segment indication output

L40

40% segment indication output

L20

20% segment indication output

LCD back plane drive

BLI

battery low indicator LED output

POL

power-on LED output

GND

power ground

Fig.2 Pin configuration.

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

FUNCTIONAL DESCRIPTION

The most important function of the SAA1501T is the
charge account in rechargeable battery systems. Both
NiCd and NiMH batteries in all sizes can be used. The
system can operate alone as a charge monitor with a
charge amount display function or, can operate in
conjunction with a charger. If the SAA1501T operates
together with a charger, it delivers a control signal at output
EN, for charge current regulation or for battery voltage
regulation.

Fast charging systems and charge current regulation

The SAA1501T is especially designed to be used in fast
charging systems. In fast charging systems, the charge
time is lowered by raising the charge current. Signal EN
controls the charger current. The counters register the
state of charge of the batteries and at the 80% level the
charge current is reduced via a smaller duty cycle
regulation of signal EN. The second (slow) level fully
charges the batteries which is not possible with the first
(fast) level. After the slow charge mode the counter
switches over to an even smaller duty cycle of EN and thus
enters the third (trickle) charge mode, to overcome the
self-discharge of the batteries.

Current sensing and charge account

The charge current is sensed by means of a very low
resistance (e.g. 70 m

) sense resistor R

(see Fig.8) to

save power at high charge rates. Via the V/I charge
converter and external resistor R

CCC

(see Fig.8), the

sensed voltage is converted into a charge current I

(the

same is applicable for the discharge current). In the I/F
converter the charge current is converted into a frequency
for up-counting the counter. For the discharge current (I

)

the converted frequency is used for down-counting. The
up and down counting is registered in counters CNT1 and
CNT2, depending on the actual charge and discharge
current levels of the batteries. This is called dynamic
charge account.

Charge display

The charge amount represented by the Coulomb counter
can be displayed via an LCD screen or via an LED
bargraph. If the charge amount is reduced to 0%, the
battery low indicator (BLI) LED is turned on at the end of a
battery discharge session. A flashing BLI, in combination
with a repeating buzzer alarm, informs the user about the
low charge state. A new charge session should then be
started.

Protections

In the temperature control block, the absolute temperature
is used as a protection to end the fast charge cycle. Fast
charging at high temperature is not permitted because of
degradation of the battery cells. If the batteries are
disconnected, an open-battery condition is recognized and
the SAA1501T enters the standby mode.

Mode detection

The mode detector detects whether there are any charge
or discharge currents, whether the system is powered,
whether loads are connected or whether the system is in
the standby mode. If power is connected, the power-on
LED (POL) is on. In the standby mode, the Coulomb
counter will count down in accordance with the
self-discharge speed of the batteries, which is temperature
controlled. The following subsections describe the various
blocks of the block diagram in more detail.

Supply and reference

During the period when V

rises from 0 V to the internal

reset level, all counters are reset. The internal reset is
released before V

reaches 1.7 V. The operating supply

voltage ranges from 2 V to the open battery level of
4.3 V (min). The characteristics are guaranteed at
V

= 3 V. In order to protect the SAA1501T against high

supply voltages during open battery in a flyback converter,
a voltage clamp circuit is made active at 6.35 V (typ). The
clamping current must not exceed 80 mA. A band gap
reference block is included to generate accurate voltages
i.e. for the oscillator. Moreover, together with R

ref

, accurate

currents are generated which are used in the I/F and V/I
converters and the oscillator block. In the standby mode
only the oscillator and the digital parts are active to limit the
discharge current of the batteries to a current level of less
than 100 mA. The circuits that are needed temporarily are
switched on and off during standby (see "Timing
characteristics" t

som

Voltage-to-current charge and discharge

In the V/I converter, the input charge current is translated
into acceptable levels for the circuit. The conversion
formula is:

; where R

CCC

> R

(see Fig.7)

arg

(

)

CCC

---------------------------------------

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

With R

CCC

, the charge efficiency can be manipulated

depending on the charge level. The restriction of the
SAA1501T is a maximum average charge current of 60

and a minimum momentary charge current of 0.6

A. The

same formula is applicable for the discharge current. The
discharge efficiency can now also be changed by R

DCC

depending on the discharge current levels, but
independent of the charge current. As both sense levels
are referenced to ground, the sensing elements could be
combined into one. The outputs are used combined as

) in the I/F converter and combined as (I

)

in the pulse width modulator block and made separately
available in the mode detector. The conversion is made
lower by a factor of 6 in the I/F converter block, thereby
enabling the use of poor leakage capacitors on pin 4. All
V/I converter pins are sensitive to capacitive loading
(C

out

conv

< 1 ms), the conversion resistors should be

mounted as close as possible to the output pins.

I/F converter

This block produces up-counts while charging and
down-counts while discharging. The I/F converter
translates the charge/discharge currents into a frequency.
This frequency is determined by

During the time period `t', the charge current, expressed as
a `Charge Parcel', will be counted in the Coulomb counters
(CNT1 and CNT2). During discharge the `Charge Parcel' is
the product of the discharge current and the `t' from the I/F
converter generated frequency. The momentary contents
of the Coulomb counter is a multiple of the `Charge
Parcels'.

Coulomb counters CNT1 and CNT2

The SAA1501T has been designed for average maximum
charge and discharge current levels of 5 C and minimum
charge and discharge current levels of 0.05 C. This means
that counter CNT1 will be full, or empty, after a minimum
time period of 12 minutes at maximum charge and
discharge currents at the recommended oscillator
frequency. Higher charge and discharge rates than 5 C
are possible, but only by changing the oscillator frequency.
It should be noted that the self-discharge time and the
display functions are influenced by a higher oscillator
frequency. The SAA1501T enables top-up charging in
order to account for the decrease of charge efficiency at
high charge rates. The SAA1501T switches to the slow
charge mode at full recognition when CNT1 is at its
maximum. As soon as the batteries are completely full
(when CNT2 is at its maximum), the SAA1501T switches

(

c d

( )

sense

)

(

osc

CCC RDCC

(

)

------------------------------------------------------------------------------------

to the trickle charge mode to overcome the self-discharge
of the batteries. The top-up charge volume of
CNT2 = 0.2

CNT1 = 0.2 C (where Q is rated as Ampere

hours of the battery). The slow and trickle charge current
levels are dependent on the k-factor. Signal EN controls
the external charger e.g. TEA1400 (see Fig.8). When an
LED bargraph display is used, the LED currents are also
considered as a battery discharge current, and therefore
influence the duty cycle of the charge current regulation
signal EN. The SAA1501T also enables temperature
protection. In the event that the battery temperature
exceeds a certain maximum temperature level
(T

battery

> T

max

), which can be set by an external NTC

resistor, the SAA1501T switches to the slow charge mode.
In the standby mode (self-discharge mode), which is
recognized by the SAA1501T in the mode detector when
both the charge and discharge currents are zero
(I

= I

= 0), the self-discharge of the batteries is registered

by counting down in 200 days (based on f

osc

= 4 kHz) if

battery

< T

self

or in 100 days (based on f

osc

= 4 kHz) if

battery

> T

self

. T

self

is also set by means of an external NTC

resistor.

Band gap generation

From the band gap voltage block, two reference voltages
are derived V

ref

and V

max

. Voltage V

ref

at pin R

ref

sets the

reference currents, I

ref1

(I/F converter); I

ref2

(mode

detector) and I

ref3

(oscillator). Voltage V

max

sets the

current I

max

which is used in the pulse width modulation

block to accurately control the charge current.

Charge current regulation

While charging, the SAA1501T produces a charge current
regulation signal EN in the pulse width modulation block
which is used for controlling an external charger. This
digital signal EN is derived from the signal produced at pin
C

. The duty cycle is determined by

in which the value of k depends on the state of the
counters CNT1 and CNT2:

CNT1 is not full; k = 1 (fast charging).

CNT1 is full; CNT2 is not full; k = 0.1 (slow charging).

CNT1 and CNT2 are full; k = 0.025 (trickle charging).

max

--------------------

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

Mode detector

This block differentiates between the available modes of
operation. The modes are given below:

Charge mode; power charge (POCH).

Discharge mode; battery load (BATLD).

Power load mode (POLD); the batteries are charged
while the load is also active.

Self discharge mode; (STANDBY).

To detect power in a regulated system (see Fig.8) the EN
signal is used for sensing. The POCH mode is recognized
when the converted charge current I

> I

ref2

(when in the

power mode, change of mode can only be recognised if
EN is HIGH). The BATLD mode is recognized when
I

> I

ref2

; the POLD mode is recognized when I

> I

ref2

and

> I

ref2

; the standby mode is recognized when I

< I

ref2

and I

< I

ref2

. In the standby mode, if the advised frequency

(4 kHz) is applied, it takes 0.5 s to determine another
mode (in all other modes, a change of mode is sensed
continuously). In all other modes an eventual change of
mode is done continuously. To save supply current during
standby, the V/I converters are switched off. With the
specific fixed intervals, the SAA1501T checks whether
power or load is connected again. This checking is
synchronized by the sensing signal of the V/I converters.
The SAA1501T can handle a DC charge current as well as
a discontinuous charge current (SMSP charger). The load
current can also be DC or interrupted, e.g. produced by a
motor. The digital filtering of both signals, to overcome
faulty mode detections, restricts the conditions in which
power and load are recognized. Because of the very
sensitive input detection level of the mode detector for a
charge current (power) in combination with the high
interference levels of motor driving, the detection level for
power (I

> I

ref2

) is raised by a factor of 25 when the

batteries are loaded.

Oscillator

As the oscillator has to operate in all modes, including the
standby mode, the current consumption of the oscillator
must be very low. The same applies for the band gap
generator block, because the band gap delivers accurate
reference voltages and currents to the oscillator block.
Apart from the low current consumption, the accuracy of
the period time is important. The period time of the
oscillator is:

osc

(

)

ref3

---------------------------

5.6

osc

ref

Prescaler/controller

In the prescaler, a new system clock is created (CLK)
which is used for all timing blocks. Many frequencies are
derived from the basic oscillator at the standard frequency
of 4 kHz (1/T

osc

), such as the self-discharge times and the

modulation frequency for the buzzer, the drive voltage
frequency for the LCD screen and the pulse trains for
temperature measurements and power/load sensing
measurements in the mode detector.

Temperature

In the temperature control block two temperature
measurements are performed. In order to switch off fast
charging when the battery temperature exceeds an
adjustable maximum temperature (T

max

), a maximum

temperature measurement is performed. A second
temperature measurement is performed in the standby
mode. This temperature measurement is input to the
temperature control block to switch over the self-discharge
rate from a count down of 200 days (based on f

osc

= 4 kHz)

if T

battery

< T

self

, to a count down rate of 100 days (based

on f

osc

= 4 kHz) if T

battery

> T

self

. In all modes the

temperature is measured periodical. The temperature
circuit which controls the above mentioned functions is a
bridge configuration synthesis, as illustrated in Fig.3.

Fig.3 Temperature circuit.

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

Display decoder driver

The counters are used to output the battery charge
amount via a decoder and driver stage to the display
outputs L100, L80, L60, L40 and L20 to drive an LCD
screen or an LED bargraph. A 64 Hz (based on
f

osc

= 4 kHz) block signal at output BP (back plane) must

be connected to the back plane of the LCD bar. If pin BP
is connected to ground, the display outputs L20 to L100
will produce signals for an LED bargraph. Output signal
POL (power-on LED) indicates when the batteries are in
the charge mode. When the counter is not at its maximum
state, POL is on and flickers at 2 Hz (based on
f

osc

= 4 kHz) when the counter is at its maximum. The

waveforms illustrated in Fig.4 depict operation of the
monitor display. The outputs BLI (battery low indication),
BUZ (buzzer) and FULL indicate the extreme status
(empty or full) of the counters and the batteries. The
waveforms of the signals BLI and BUZ if one switches over
from BATLD to standby when BLI is active, are given in
Fig.4.

The BLI sequence is as follows. If during discharge the
charge state falls below 0%, the red BLI LED is turned on.
Changing mode from discharge to standby means that the
BLI LED and the buzzer (BUZ) are activated as indicated
in Fig.4. If after a 0% passing recharge is activated, the red
BLI LED is turned on again for as long as the counter
remains below 10%. Switch-over in the 0 to 10% range to
standby will activate BLI and BUZ again.

The LEDs of the LED bargraph are activated as a result of
each operational mode change, starting with a step-up
pattern. Step-up means that LEDs are activated
successively one after the other, in accordance with the
charge status each

s (based on f

osc

= 4 kHz). After the

step-up, the LEDs will be on for 8 s (based on
f

osc

= 4 kHz), except for the POCH mode, where the LEDs

will be on continuously to inform the user about the charge
state of the batteries. The LCD display is, apart from the
LED mode, always visible.

Figure 5 shows the legend for Fig.6. Figure 6 shows the
operation of the monitor display.

BUZ

Fig.4 BLI and buzzer timing.

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

Open battery protection

Open battery protection is active when V

= 4.5 V (typ.).

The SAA1501T will then react as if the system is in the
standby mode. This means that the LEDs are turned off in
the LED mode, in the LCD mode the flickering is stopped
and the enable pin (EN) is switched to floating.

Testing

A user test facility is built-in for checking if the LCD and/or
LED displays are mounted correctly. Pin R

CCC

is used as

a test pin. Raising the voltage above 1 V during the set-up
time will activate the test. The test mode can only be
started in the standby mode. In the test mode all counters
are reset and will be active successively in the sequence
BLI, L20, L40, L60, L80, L100 and FULL with an interval
period determined by T

osc

. The test mode can be exited via

the following methods:

Power-on; the Coulomb counter retains the latest data
displayed.

Automatically after the test cycle time; the Coulomb
counter is reset.

Fig.5 Legend for Fig.6.

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

LIMITING VALUES

In accordance with the Absolute Maximum Rating System (IEC 134). All voltages with respect to GND (pin 24); input
currents are positive; pins 5, 6 and 21 are not allowed to be voltage driven; the voltage ratings are valid provided other
ratings are not being violated.

QUALITY SPECIFICATION

In accordance with SNW-FQ-611 part E. The numbers of the quality specification can be found in the "

Quality Reference

Handbook". The Handbook can be ordered using the code 9398 510 63011.

THERMAL CHARACTERISTICS

SYMBOL

PARAMETER

CONDITIONS

MIN.

MAX.

UNIT

supply voltage

0.5

+5.5

input voltage at pins 9 to 12

0.5

+1.0

input voltage at pins 2 to 4, 13 to 20, 22
and 23

0.5

voltage difference between pins 10 and
7 and between pins 9 and 8

2.0

+2.0

supply current

GND

power ground supply current

supply current at pins 5 to 8

tot

total power dissipation

amb

= 70

0.75

stg

storage temperature

+150

junction temperature

+150

amb

operating ambient temperature

+75

SYMBOL

PARAMETER

VALUE

UNIT

th j-a

thermal resistance from junction to ambient in free air

K/W

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

CHARACTERISTICS
V

= 3 V; T

amb

= 25

C; R

ref

= 51.5 k

(0.1%); C

osc

= 820 pF (0.1%); R

CCC

= R

DCC

= 3.65 k

(0.1%); R

max

= 3.48 k

(0.1%); I

ref

= V

ref

; I

max

= V

max

; the minimum and maximum values are 4 sigma limits; unless otherwise

specified.

SYMBOL

PARAMETER

CONDITIONS

MIN.

TYP.

MAX.

UNIT

Supply

supply voltage

note 1

2.0

3.0

4.3

CC(ir)

supply voltage internal
reset

1.2

1.7

supply current

= I

= 60

0.6

1.7

CCstb

supply current in standby
mode

CSI

= V

DSI

= 0 V

100

ref

reference voltage

note 2

204

211

217

ref

reference current

notes 1 and 2

3.5

max

maximum voltage

note 2

204

211

217

temperature coefficient of
reference voltage

T = 0 to 100

100

clamp

clamping level voltage

= 50 mA

5.8

6.3

6.8

Voltage-to-current charge/discharge

voltage-to-current
charge/discharge current
accuracy

= 7 mV; V

= 1.5 V

259

324

389

= 7 mV; V

= 1.5 V

262

328

394

= 200 mV; V

= 1.5 V

8.93

9.13

9.32

= 200 mV; V

= 1.5 V

8.93

9.13

9.32

voltage-to-current
charge/discharge current
accuracy

= 7 mV; R

max

= 400 k

;

k = 0.025

1.55

1.94

2.32

= 7 mV; R

max

= 400 k

;

k = 0.025

1.57

1.97

2.36

= 200 mV;

max

= 400 k

; k = 0.025

53.5

54.7

= 200 mV;

max

= 400 k

; k = 0.025

53.5

54.7

relative current accuracy
of voltage-to-current in
charge counter capacitor

= V

= 200 mV

1.0

2.5

i(s)

input sense voltage at
pins 9 and 10

CC(max)

= 3.7 V; note 1

1.6

3.7 < V

< 4.4 V; note 1

2.1

o(s)

DC output sense current
(pins 8 and 7)

0.6

offset voltage

1.8

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

I/F converter

multiplication factor for
I

ref1

= a

ref

(where a is constant);
V

= 1.26 V; idle mode

2.35

2.5

2.65

clamp

clamping voltage (pin 4)

= 0; I

= 60

= 10

0.7

0.9

1.1

CCC(H)

HIGH level reference
voltage (pin 4)

1.58

1.66

1.74

CCC(L)

LOW level reference
voltage (pin 4)

1.26

1.33

1.4

Pulse width modulator

ACC

accuracy for I

max

at C

15 < I

max

< 60

max

maximum DC current

max

= V

max

; note 1

0.6

max

k factor

k = 1; V

= 1.5 V; idle mode

0.95

0.98

1.01

k = 0.1; V

= 1.5 V; idle

mode

0.094

0.099

0.104

k = 0.025; V

= 1.5 V;

idle mode

0.023

0.025

0.027

CCY

start up-clamping voltage
(pin 3)

= 10

A; I

= 0

0.7

0.9

1.1

CCY

clamping voltage (pin 3)

open-circuit at pin 3;
pin 5 = V

;

) = 60

0.6

CCY(H)

HIGH level switching
voltage

1.60

1.77

1.86

CCY(L)

LOW level switching
voltage

1.28

1.32

1.37

3-state enable current

= 1.5 V

Mode detector

ref2

mode detection level at
pins 7 and 8

ref2

ref

(where e is constant)

0.15I

ref

ref4

mode detection level at
pin 7

ref4

ref2

;

in modes POLD and BATLD

25I

ref2

Oscillator (pin 13)

charge amount

ref1(sink)

clk

142

150

158

discharge amount

ref1(source)

clk

142

150

158

difference between
charge and discharge
charge amount

0.95

1.0

1.05

multiplication factor for
I

ref3

= b

ref

(where b is constant)

0.75

osc

voltage swing
HIGH-to-LOW transition

440

SYMBOL

PARAMETER

CONDITIONS

MIN.

TYP.

MAX.

UNIT

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

osc

oscillator frequency

3.9

4.3

4.7

kHz

Temperature control (pins 11 and 12)

input voltage

900

TEMP2

TEMP1

detection at T

max

= V

= 300 mV

9.7

10.0

10.3

TEMP2

TEMP1

detection at T

self

= V

= 300 mV

multiplication factor for
I

TEMP1

= c

ref

(where c is constant);
V

TEMP1

= V

TEMP2

= 300 mV

0.45

0.54

0.63

multiplication factor for
I

TEMP2

= d

ref

(where d is constant);
V

TEMP1

= V

TEMP2

= 300 mV

4.5

5.4

6.3

Open battery protection

CC(ob)

open-battery level voltage

4.3

4.5

4.65

Testing

test

test level voltage

1.0

2.0

Display decoder driver

OL1

LOW level output current
(pin 20 LED),
(LED 20 is on)

= 0.6 V; L40 to L100 off;

= 2.4 V

OBP

output LED sense current
(pin 21 LED),
(LED 20 is on)

OBP

= 0.1 V; L40 to L100

off; V

= 2.4 V

100

LED(CF)

LED current
compensation factor

OL1

OBP

; V

= 2.4 V

110

121

132

OL2

LOW level output current
(pins 20 to 16 LED),
(all LEDs are on)

all LEDs on; V

= 0.7 V;

= 2.8 V

7.5

OBP(tot)

total output sense current
(pins 21)

OBP

= 0.1 V; V

= 2.8 V;

L20 to L100 on

350

452

560

LED(CF)

LED current
compensation factor

OL2

OBP(tot)

115

125

135

output current
(pins 20 to 16 LCD)

= 0.5 V; V

= 2.8 V

350

480

640

OL(14,15)

LOW level output current
(pins 14 and 15)

= 0.4 V; V

= 2.4 V

0.9

1.2

1.7

OL(22,23)

LOW level output current
(pins 22 and 23 LED)

= 0.4 V; V

= 2.1 V

OL(21)

LOW level output current
(pin 21 LCD)

= 0.4 V; V

= 2.8 V

572

849

1214

HIGH level output current
(pins 20 to 16 LED)

= 2.4 V; V

= 2.8 V

261

378

526

OH(21)

HIGH level output current
(pin 21 LED)

= 2.4 V; V

= 2.8 V

239

378

565

SYMBOL

PARAMETER

CONDITIONS

MIN.

TYP.

MAX.

UNIT

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

TIMING CHARACTERISTICS

Notes

; where V

osc

= 440 mV and I

ref3

= 0.75.

2. Applies to all converters and enable signal.

3. For charge current AC or DC: f >

osc

4. For discharge current AC: f >

osc

SYMBOL

PARAMETER

CONDITIONS

VALUE

osc

oscillator cycle time

note 1

osc

= 2C

osc

ref3

clk

clock cycle time

64t

osc

som

sense operation mode time

note 2

1.5

osc

som(p)

sense operation mode period
time

note 2

osc

rec

recognition time

power; note 3

>32t

osc

load; note 4

>20t

osc

self

self discharge counter time

battery

> T

self

(100 days at f

osc

= 4 kHz)

osc

battery

> T

self

(200 days at f

osc

= 4 kHz)

osc

battery(s)

battery temperature
measurement sense time

osc

battery(p)

battery temperature
measurement period time

osc

display test set-up time

osc

< t < 1.5

osc

interval display test time

osc

period display test time

1.5

osc

su:LED

LED set-up time

osc

LED(ON)

LEDs-on time

after change of mode
(except POCH mode)

osc

drive voltage frequency for back
plane

osc

BUZ

modulation frequency for auto
buzzer

osc

ref3

-----------

December 1994

Philips Semiconductors

Objective specification

Battery charge level indicator

SAA1501T

SOLDERING

Plastic small-outline packages

Y WAVE

During placement and before soldering, the component
must be fixed with a droplet of adhesive. After curing the
adhesive, the component can be soldered. The adhesive
can be applied by screen printing, pin transfer or syringe
dispensing.

Maximum permissible solder temperature is 260

C, and

maximum duration of package immersion in solder bath is
10 s, if allowed to cool to less than 150

C within 6 s.

Typical dwell time is 4 s at 250

A modified wave soldering technique is recommended
using two solder waves (dual-wave), in which a turbulent
wave with high upward pressure is followed by a smooth
laminar wave. Using a mildly-activated flux eliminates the
need for removal of corrosive residues in most
applications.

Y SOLDER PASTE REFLOW

Reflow soldering requires the solder paste (a suspension
of fine solder particles, flux and binding agent) to be

applied to the substrate by screen printing, stencilling or
pressure-syringe dispensing before device placement.

Several techniques exist for reflowing; for example,
thermal conduction by heated belt, infrared, and
vapour-phase reflow. Dwell times vary between 50 and
300 s according to method. Typical reflow temperatures
range from 215 to 250

Preheating is necessary to dry the paste and evaporate
the binding agent. Preheating duration: 45 min at 45

EPAIRING SOLDERED JOINTS

(

BY HAND

HELD SOLDERING

IRON OR PULSE

HEATED SOLDER TOOL

)

Fix the component by first soldering two, diagonally
opposite, end pins. Apply the heating tool to the flat part of
the pin only. Contact time must be limited to 10 s at up to
300

C. When using proper tools, all other pins can be

soldered in one operation within 2 to 5 s at between 270
and 320

C. (Pulse-heated soldering is not recommended

for SO packages.)

For pulse-heated solder tool (resistance) soldering of VSO
packages, solder is applied to the substrate by dipping or
by an extra thick tin/lead plating before package
placement.

DEFINITIONS

LIFE SUPPORT APPLICATIONS

These products are not designed for use in life support appliances, devices, or systems where malfunction of these
products can reasonably be expected to result in personal injury. Philips customers using or selling these products for
use in such applications do so at their own risk and agree to fully indemnify Philips for any damages resulting from such
improper use or sale.

Data sheet status

Objective specification

This data sheet contains target or goal specifications for product development.

Preliminary specification

This data sheet contains preliminary data; supplementary data may be published later.

Product specification

This data sheet contains final product specifications.

Limiting values

Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 134). Stress above one or
more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation
of the device at these or at any other conditions above those given in the Characteristics sections of the specification
is not implied. Exposure to limiting values for extended periods may affect device reliability.

Application information

Where application information is given, it is advisory and does not form part of the specification.

Philips Semiconductors

Philips Semiconductors a worldwide company

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For all other countries apply to: Philips Semiconductors,
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Telex 35000 phtcnl, Fax. +31-40-724825

SCD35

All rights are reserved. Reproduction in whole or in part is prohibited without the
prior written consent of the copyright owner.

The information presented in this document does not form part of any quotation
or contract, is believed to be accurate and reliable and may be changed without
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other industrial or intellectual property rights.

Printed in The Netherlands

373061/1500/01/pp20

Date of release: December 1994

Document order number:

9397 743 50011

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