IMP525
IMP525
Sing
Sing
le Cell Batt
le Cell Batt
er
er
y P
y P
o
o
w
w
er
er
ed
ed
Electr
Electr
oluminescent Lam
oluminescent Lam
p
p
Dr
Dr
iv
iv
er/In
er/In
v
v
er
er
t
t
er
er
x
Audio/TV remote control units
x
Pagers/Cellular phones
x
PDAs
x
Clocks and radios
x
Portable GPS receivers
x
LCD modules
x
Toys
x
Wide operating voltage range - from 0.9V to 2.5V
x
Simple design requires few passive components
x
112V peak-to-peak typical AC output voltage
x
Adjustable output frequency controls lamp
color and power consumption
x
Adjustable converter frequency minimizes
circuit power consumption
x
Disable mode extends battery life
x
Disable current under 2
A
x
Compact MicroSO package option
Key Features
Applications
Block Diagram
+
525_01.eps
V
DD
1
L
X
4
C
S
3
V
A
7
V
B
6
R
SW-OSC
2
Switch
Oscillator
Regulation
Control
IMP525
Bridge
Output
Driver
Q
Q
Q
V
REF
Lamp Drive
Oscillator
C
GND
5
R
EL-OSC
8
Q
The IMP525 is an Electroluminescent (EL) lamp driver designed for sys-
tems that must operate below 1 volt. The input supply voltage range is
0.9V to 2.5V. Typical output lamp drive voltage is 112V. All four EL lamp-
driving functions are on-chip. These are the switch-mode power supply,
its high-frequency oscillator, the high-voltage H-bridge lamp driver and
its low-frequency oscillator. EL lamps of up to 6nF capacitance can be dri-
ven to high brightness.
The circuit requires few external components; one inductor, one diode,
one capacitor and two resistors. The resistors set the frequency for the
two oscillators.
A disable mode puts the chip into a low current-drain state. When dis-
abled, quiescent current drops to 2
A maximum with a V
DD
of 1.5V. The
chip can be disabled by connecting R
SW
, the oscillator frequency setting
resistors, to ground. A disable pad, accessible only on the die, can also be
used to disable the driver.
An internal circuit shuts down the switching regulator when the lamp
drive voltage exceeds 112V peak-to-peak. This conserves power and
extends battery life.
The IMP525 is available in MicroSO and SO-8 packages and in die form.
P
OWER
M
ANAGEMENT
IMP, Inc.
San Jose, CA
408-432-9100/www.impweb.com
IMP525
IMP525
Parameter
Symbol Conditions
Min
Typ
Max
Units
ON-resistance of MOS Switch
R
DS(ON)
I = 50mA
15
Operating Voltage
0.9
2.5
V
Output Voltage at C
S
V
CS
V
DD
= 1.5V, See Figure 1, Table 1
52
58
65
V
Output Voltage at C
S
V
CS
V
DD
= 0.9V, See Figure 1, Table 2
50
V
Output Voltage Peak-to-Peak
V
A
-V
B
V
DD
= 1.5V, See Figure 1
104
112
124
V
P-P
Quiescent V
DD
Supply Current, Disabled
I
QDIS
Disable = HIGH
70
nA
(Disable pin available on die only)
Quiescent V
DD
Supply Current, Disabled
I
QDIS
R
SW-OSC
= GND
1.0
2.0
A
V
DD
= 1.5V
Input Current at V
DD
Pin
I
DD
V
DD
= 0.9V to 1.5V
1.5
mA
Input Current: I
DD
Plus Inductor Current
I
IN
V
DD
= 1.5V
23
32
mA
V
A-B
Output Drive Frequency
f
EL
V
DD
= 1.5V, See Figure 1, Table 1
500
Hz
Boost Converter Switching Frequency
f
SW
V
DD
= 1.5V, See Figure 1, Table 1
26
kHz
Switching Duty Cycle
D
SW
V
DD
= 1.5V, See Figure 1
87.5
%
Disable Input LOW Voltage
V
DISL
GND
0.2
V
(Disable pin available on die only)
Disable Input HIGH Voltage
V
DISH
V
DD
-0.5V
V
DD
V
(Disable pin available on die only)
Ordering Information
Pin Configuration
4
L
X
3
C
S
2
R
SW-OSC
1
V
DD
5
GND
6
V
B
7
V
A
8
R
EL-OSC
525_02.eps
IMP525
SO/MicroSO
Part Number
Input Voltage
Regulated Output Voltage
Temperature Range
Pins-Package
IMP525EMA
0.9V to 2.5V
YES
40
C to +85
C
8-MicroSO
IMP525ESA
0.9V to 2.5V
YES
40
C to +85
C
8-SO
IMP525/D
0.9V to 2.5V
YES
25
C
Dice
2
Absolute Maximum Ratings
Supply Voltage, V
DD
, V
RSW-OSC
and V
REL-OSC
. . 0.5V to +3.5V
Storage Temperature Range . . . . . . . . . . . . . . . . 65C to +150C
Power Dissipation (SO package) . . . . . . . . . . . . 400mW
Power Dissipation (MicroSO package) . . . . . . . 300mW
Unless otherwise noted, V
DD
= 1.5V, R
SW
= 1M
, R
EL
= 1.0M
, and T
A
= 25C.
Note: All voltages are referenced to GND.
These are stress ratings only and functional operation is not implied.
Exposure to absolute maximum ratings for prolonged time periods may
affect device reliability.
Electrical Characteristics
3
IMP525
IMP525
Typical Characteristics
Frequency (Hz)
R
EL
(M
)
EL Lamp Drive Frequency
525_08.eps
V
DD
= 1.5V
T
A
= 25
C
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0
400
800
1200
1600
2000
2400
Frequency (kHz)
R
SW
(M
)
525_10.eps
0
0.5
1.0
1.5
2.0
2.5
3.0
0
25
50
75
100
125
150
Boost Converter
Switching Frequency
V
DD
= 1.5V
T
A
= 25
C
Period (ms)
R
EL
(M
)
525_07.eps
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0
1
2
3
4
5
6
7
8
EL Lamp Drive Period
V
DD
= 1.5V
T
A
= 25
C
Period (ms)
R
SW
(M
)
525_09.eps
0
0.5
1.0
1.5
2.0
2.5
3.0
0
25
50
75
100
Boost Converter
Switching Period
V
DD
= 1.5V
T
A
= 25
C
IMP525
IMP525
4
Pin Descriptions
Pin Number
Name
Function
1
V
DD
Positive voltage supply for the IMP525. Inductor L may be connected here or to a
separate supply.
2
R
SW-OSC
Switch-mode resistor pin. Switching frequency is determined by external resistor R
SW
,
connected between pin 2 and V
DD
.
3
C
S
Boost converter storage capacitor. The voltage across the EL lamp is equal to twice the
voltage at C
S
.
4
L
X
Connection to flyback inductance, L.
5
GND
Ground pin.
6
V
B
EL lamp drive. The lamp is connected to a high-voltage bridge circuit with V
B
providing
the complementary connection to V
A
.
7
V
A
EL lamp drive. (See above)
8
R
EL-OSC
The EL lamp oscillator frequency-setting pin. The frequency is controlled by resistor R
EL
,
connected from pin 8 to V
DD
.
Disable Pad
DIS
Available only in die form. Setting DIS HIGH disables the chip.
External Component
Description and Selection Guide
Diode
A fast reverse recovery diode, with BV > 100, such as a 1N4148.
Capacitor C
S
The high voltage capacitor that stores the inductive energy transferred through the
catch diode. A 100 volt capacitor between 10nF and 100nF is recommended.
Resistor R
EL
The EL lamp oscillator frequency-setting resistor. R
EL
is connected between pin 8 and V
DD
,
providing a frequency inversely proportional to R
EL
; as R
EL
increases, the EL lamp frequency
decreases along with the current drawn by the lamp. Lamp color is also determined by this
frequency. A 1M
resistor between the R
EL-OSC
pin and the V
DD
supply results in a lamp
frequency around 500Hz.
Resistor R
SW
Switching Oscillator frequency-setting resistor. R
SW
is connected between the R
SW-OSC
pin and
the V
DD
supply. The switching frequency is inversely proportional to the resistor value, dropping
as the resistance increases.
Capacitor C
SW
This is an optional noise-suppression capacitor connected from ground to the R
SW-OSC
pin.
A 100pF capacitor is recommended.
Inductor L
The inductor provides the voltage boost needed by means of inductive "flyback". The internal
MOSFET switch alternately opens and closes the ground connection for the inductor at the
L
X
pin. When the switch opens, the inductor potential will forward-bias the diode
and the current will pass through to the storage capacitor C
S
, charging it to a high voltage.
As the value of the inductor is increased, the switching frequency set by R
SW
should also be
increased to prevent saturation. In general, smaller value inductors that can handle more current
are more desirable when larger-area EL lamps must be driven.
A small electrolytic capacitor (10
F, 16V), normally present across the inductor supply V
IN
,
will likely eliminate the need for C
SW
.
External Components
5
IMP525
IMP525
+
V
DD
R
SW-OSC
C
S
L
X
R
EL-OSC
V
A
V
B
GND
8
7
6
5
1
2
3
4
IMP525
R
EL
R
SW
C
S
V
DD
0.1
F
1
1N4148
D
L
3nF
Note:
1. Larger values may be required depending upon supply impedance.
525_03.eps
0.1
F
100V
ON = V
DD
OFF = 0V
Figure 1. Test Circuit
Test Circuit
Figure 1 shows the IMP525 configured to drive an EL lamp,
represented as a 3nF capacitor.
Component
Connections
Value
Description
R
SW
V
DD
, R
SW-OSC
1M
Boost converter oscillator bias resistor
R
EL
V
DD
, R
EL-OSC
1M
EL lamp driver oscillator bias resistor
L
V
DD
, L
X
2
330
H
2
Boost converter inductor
C
S
C
S
, GND
0.1
F/100V
Boost converter storage capacitor
D
L
X
, C
S
1N4148
Switching diode
Table 1. V
IN
= 1.5V
Notes. 2. Murata LQH4N331K04 (8.2
max. DCR)
Component
Connections
Value
Description
R
SW
V
DD
, R
SW-OSC
1.0M
Boost converter oscillator bias resistor
R
EL
V
DD
, R
EL-OSC
2.62M
EL lamp driver oscillator bias resistor
L
V
DD
, L
X
3
680
H
3
Boost converter inductor
C
S
C
S
, GND
0.1
F/100V
Boost converter storage capacitor
D
L
X
, C
S
1N4148
Switching diode
Table 2. V
IN
= 0.9V
Notes. 3. Coilcraft DS1608C-684 (2.2
max. DCR)
Application Information
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