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PT5800 Series

18-A 5-V Input Adjustable
Integrated Switching Regulator

SLTS171A JANUARY 2003 - REVISED - MARCH 2003

Standard Application

= Required 820µF

out

= Required 330µF

Ordering Information

PT5801

H = 3.3 Volts

PT5802

H = 2.5 Volts

PT5803

H = 1.8 Volts

PT5804

H = 1.5 Volts

PT5805

H = 1.2 Volts

PT5806

H = 1.0 Volts

Function

Adjust

Inhibit*

Margin Dn*

Margin Up*

Sense()

GND

out

Sense(+)

Features

5V Input

18A Output Current

DSP Compatible

Low-Profile (8mm)

>90% Efficiency

Output Margin Control (±5%)

Adjustable Output Voltage

On/Off Inhibit Function

Pre-Bias Startup Capability

Pin-Out Information

* Denotes negative logic:
Open = Normal operation
Ground = Function active

Description

The PT5800 ExcaliburTM series of integrated

switching regulators (ISRs) combines outstand-
ing power density with a comprehensive list of
features. They are an ideal choice for applications
where board space is a premium and performance
cannot be compromised. These modules provide
18A of output current, yet are housed in a low-
profile, 18-pin package that is almost half the
size of the previous product generation. The
integral copper case construction requires no
heatsink, and offers the advantages of solderabil-
ity and a small footprint (0.736 in² for suffix `N').
Both through-hole and surface mount pin con-
figurations are available.

The PT5800 series operates from a 5-V input

bus and provides a convenient point-of-load power
source for the industry's latest high-performance
DSPs and microprocessors. The series includes
output voltage options as low as 1.0VDC.

Other features include external output voltage

adjustment, a ±5% margin control, on/off inhibit,
short circuit protection, thermal shutdown, and a
differential remote sense.

PT Series Suffix

(PT1234

)

Case/Pin

Order

Package

Configuration

Suffix

Code

Vertical

(EPP)

Horizontal

(EPQ)

SMD

(EPS)

(Reference the applicable package code draw-
ing for the dimensions and PC board layout)

Over-Current Protection

Over-Temperature Protection

Small Footprint
(0.736 in², Suffix `N')

Surface Mount Compatible

IPC Lead Free 2

PT5800

Adjust

Margin Up

Margin Dn

913

1417

5, 6, 7

O
A
D

820µF
(Required)

OUT

330µF
(Required)

Inhibit

GND

OUT

Sense(+)

Sense()

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PT5800 Series

18-A 5-V Input Adjustable
Integrated Switching Regulator

Specifications

(Unless otherwise stated, T

=25°C, V

=5V, C

=820µF, C

out

=330µF, and I

max)

PT5800 SERIES

Characteristics

Symbols

Conditions

Min

Typ

Max

Units

Output Current

=5V

Input Voltage Range

Over I

range

4.5

5.5

Set-Point Voltage Tolerance

tol

±2

Temperature Variation

Reg

temp

40°C <T

< +85°C

±0.5

Line Regulation

Reg

line

Over V

range

±8

Load Regulation

Reg

load

Over I

range

±5

Total Output Variation

Reg

tot

Includes set-point, line, load,

±3

40°C

+85°C

Efficiency

=12A

PT5801 (3.3V)

PT5802 (2.5V)

PT5803 (1.8V)

PT5804 (1.5V)

PT5805 (1.2V)

PT5806 (1.0V)

Ripple (pk-pk)

20MHz bandwidth

mVpp

Transient Response

1A/µs load step, 50 to 100% I

max,

Recovery Time

µSec

over/undershoot

100

Over-Current Threshold

TRIP

Reset, followed by auto-recovery

Output Voltage Adjust

adj

With V

Adjust

±15

(1)

With Margin Up/Dn

±5

Switching Frequency

Over V

and I

ranges

250

300

350

kHz

Inhibit Control (pin 2)

Referenced to GND (pins 913)

Input High Voltage

0.5

Open

(2)

Input Low Voltage

0.2

0.8

Input Low Current

Pin 2 to GND

µA

Standby Input Current

standby

Pin 2 to GND

External Input Capacitance

820

(3)

µF

External Output Capacitance

out

330

(4)

5,000

µF

Operating Temperature Range

Over V

range

(4)

(5)

°C

Over-Temperature Protection

OTP

Measured at center of case, auto-reset

110

°C

Solder Reflow Temperature

reflow

Surface temprature of module pins or case

215

(6)

°C

Storage Temperature

125

°C

Reliability

MTBF

Per Bellcore TR-332

5.8

Hrs

50% stress, T

=40°C, ground benign

Mechanical Shock

Mil-STD-883D, Method 2002.3

500

Half Sine, mounted to a fixture

Mechanical Vibration

Mil-STD-883D, Method 2007.2,

Suffix N

(7)

20-2000 Hz, PCB mounted

Suffixes A, C

(7)

Weight

grams

Flammability

Materials meet UL 94V-0

Notes: (1) This is a typical value. For the adjustment limits of a specific model consult the related application note on output voltage adjustment.

(2) The Inhibit control (pin 2) has an internal pull-up to V

, and if left open-circuit the module will operate when input power is applied. A small low-

leakage (<100nA) MOSFET is recommended to control this input. See application notes for more information.

(3) An 820µF electrolytic input capacitor is required for proper operation. This capacitor must be rated for a minimumm of 0.7 Arms of ripple current.
(4) For operation below 0°C, C

OUT

must have stable characteristics. Use either low-ESR tantalum or Oscon® type capacitors.

(5) See SOA curves or consult factory for the appropriate derating.
(6) During solder reflow of SMD package version do not elevate the module case, pins, or internal component temperatures above a peak of 215°C. For

further guidance refer to the application note, "Reflow Soldering Requirements for Plug-in Power Surface Mount Products," (SLTA051)

(7) The case pins on the through-hole package types (suffixes N & A) must be soldered. For more information see the applicable package outline drawing.

SLTS171A JANUARY 2003 - REVISED - MARCH 2003

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Note A:

Characteristic data has been developed from actual products tested at 25°C. This data is considered typical data for the ISR.

Note B:

SOA curves represent operating conditions at which internal components are at or below manufacturer's maximum rated operating temperatures.

Efficiency vs Output Current

Power Dissipation vs Output Current

Performance Data; V

=5V

(See Note A)

Output Ripple vs Output Current

PT5800 Series

18-A 5-V Input Adjustable
Integrated Switching Regulator

Pin Descriptions

Vin:

The positive supply voltage input for the module

with respect to the common ground (GND).

Vout:

This is the regulated output voltage from the mod-

ule with respect to the common ground (GND).

GND:

The common ground node to which the input,

output, and external control signals are referenced.

Sense():

Provides the regulator with the ability to sense

the set-point voltage directly across the load. For opti-
mum output voltage accuracy this pin should always be
connected to GND, even for applications that demand a
relatively light load.

Sense(+):

When used with Sense(), the regulation circuitry

will compensate for voltage drop between the converter
and the load. The pin may be left open circuit, but con-
necting it to V

out

will optimize load regulation.

Inhibit*:

This is an open-collector (open-drain) negative

logic input, referenced to GND. Pulling this pin to
GND disables the module's output voltage. If Inhibit* is

left open circuit, the output will be active whenever a
valid input source is applied.

Adjust:

This pin is used to trim the output voltage

over a typical range of ±15% of nominal. The adjust-
ment method uses an external resistor. The resistor is
connected from V

Adjust to either the (-)Sense or (+)Sense,

in order to adjust the output either up or down, respec-
tively. Consult the related application note for the adjust
limits of a specific part.

Margin Dn*:

When this open-collector (open-drain) input

is asserted to GND, the output voltage is automatically
decreased by 5% from the nominal. This feature is used in
applications where the load circuit must be tested for
operation at the extreme values of its supply voltage
tolerance.

Margin Up*:

This is an open-collector (open-drain) input.

When this is asserted to GND, the output voltage is
automatically increased by 5% from the nominal.

Typical Characteristics

100

Iout (A)

Efficiency - %

PT5801
PT5802

PT5803
PT5804

PT5805

PT5806

Iout (A)

Ripple - mV

PT5802
PT5801
PT5803
PT5804
PT5805
PT5806

Iout (A)

Pd - Watts

Iout (A)

Ambient Temperature (°C)

200LFM
120LFM
60LFM
Nat conv

Airflow

Safe Operating Curves; V

=5V

(See Note B)

SLTS171A JANUARY 2003 - REVISED - MARCH 2003

Application Notes

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PT5800 & PT5810 Series

With the sense leads connected, the difference between
the voltage measured at V

out

and GND pins, and that

measured from Sense(+) to Sense(), is the amount of IR
drop being compensated by the regulator. This should
be limited to 0.6V. (0.3V maximum between pins 17 &
18, and also between pins 8 & 9).

Note: The remote sense feature is not designed to compensate
for the forward drop of non-linear or frequency dependent
components that may be placed in series with the converter
output. Examples include OR-ing diodes, filter inductors,
ferrite beads, and fuses. When these components are enclosed
by the remote sense connections they are effectively placed
inside the regulation control loop, which can adversely affect
the stability of the regulator.

Over-Current Protection

To protect against load faults, the regulators incorporate
output over-current protection. Applying a load that
exceeds the regulator's over-current threshold (see data
sheet specifications) will cause the regulated output to
shut down. Following shutdown the ISR will periodically
attempt to recover by initiating a soft-start power-up.
This is often described as a "hiccup" mode of operation,
whereby the module continues in the cycle of successive
shutdown and power up until the load fault is removed.
During this period, the average current flowing into the
fault is significantly reduced. Once the fault is removed,
the converter automatically recovers and returns to nor-
mal operation.

Over-Temperature Protection

An on-board temperature sensor protects the module's
internal circuitry against excessively high temperatures.
A rise in the internal temperature may be the result of a
drop in airflow, or a high ambient temperature. If the
internal temperature exceeds the OTP threshold (see
data sheet specifications), the regulator's Inhibit* control
is automatically pulled low. This disables the regulator,
allowing the output voltage to drop to zero as the exter-
nal output capacitors are discharged by the load circuit.
The recovery is automatic, and begins with a soft-start
power up. It occurs when the the sensed temperature
decreases by about 10°C below the trip point.

Note: The over-temperature protection is a last resort mecha-
nism to prevent thermal stress to the regulator. Operation at
or close to the thermal shutdown temperature is not recom-
mended and will reduce the long-term reliability of the module.
Always operate the regulator within the specified Safe Operating
Area (SOA) limits for the worst-case conditions of ambient
temperature and airflow.

Differential Remote Sense

Connecting the Sense(+) and Sense(-) pins to the load
circuit allows the regulator to compensate for limited
amounts of `IR' voltage drop. This voltage drop is caused
by current flowing through the connection resistance
between the regulator and the `point of regulation' some
distance away. Leaving the sense pins disconnected will
not damage the regulator or load circuitry. An internal
15

resistor, connected between each sense pin and its

corresponding output node, keeps the output voltage in
regulation. However, it is important to connect Sense()
to GND locally, as this provides a return path for the
regulator's internal bias currents.

Operating Features and System Considerations
for the PT5800 & PT5810 Regulator Series

The PT5800 (5-V input) and the PT5810 (3.3-V input)
series of integrated switching regulators (ISRs) provide
step-down voltage conversion for output loads of up to
18A.

Power up & Soft-Start Timing

Following either the application of a valid input source
voltage, or the removal of a ground signal to the Inhihit*
control pin (with input power applied), the regulator will
initiate a soft-start power up. The soft start slows the
rate at which the output voltage rises, and also introduces a
short time delay, t

(approx. 2ms). Figure 1-1 shows the

power-up characteristic of a PT5801 (3.3V) with a 10-A
load.

Vo (2V/Div)

Vin (2V/Div)

HORIZ SCALE: 5ms/Div

Figure 1-1

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Application Notes

Startup of the PT5800 & PT5810 Series ISRs
with Back-Feeding Source (Pre-Bias Capability)

In complex digital systems an external voltage can
sometimes be present at the output of the regulator
during power up. For example, this voltage may be
backfed through a dual-supply logic component such as
an FPGA or ASIC. Another path might be via a clamp
diode (to a lower supply voltage) as part of a power-up
sequencing implementation.

Although the PT5800 (5-V input) and PT5810 (3.3-V
input) series of regulators will sink current under steady-
state operating conditions, they will not do so during
startup

as long as certain conditions are maintained

This feature allows these regulators to start up while an
external voltage is simultaneously applied to the output.
Figure 2-1 is an application schematic that demonstrates
this capability. The waveforms in Figure 2-2 show the
behavior of the circuit as input power is applied. Note
that the plot of the regulator output current (I

) is approxi-

mately zero up to the timestamp `A', even though a voltage
is initially backfed to the output via the 3.3-V input supply
and diodes D

& D

. The regulator sources current

when

it begins raising the output above the back-fed voltage to
its nominal regulation value.

Notes

1. Startup includes both the application of a valid input

source voltage, or the removal of a ground signal from
the Inhibit* control (pin 2) with a valid input source
applied. The output of the regulator is effectively off
(tri-state), during the period that the Inhibit* control is
held low.

Vin (1V/Div)

Vo (1V/Div)

Io (5A/Div)

HORIZ SCALE 5ms/Div

Figure 2-2; Power-up Waveforms with Back-Feeding Source

Figure 2-1; Schematic Demonstrating Startup into Pre-Bias Capability

PT5812

1417

913

OUT

GND

out

(3.3VDC)

COM

(2.5V)

Sense(+)

Sense()

2. To ensure that the regulator does not sink current, the

input voltage must always be greater or equal to the
output voltage throughout the power-up and power-down
sequence.

3. If an external source backfeeding the regulator's output

is greater than the nominal regulation voltage, the output
will begin sinking current at the end of its soft-start
power-up sequence. If this current exceeds the rated
output, the module could be overstressed.

PT5800 & PT5810 Series

Application Notes

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Table 3-1; Input/Output Capacitors

Capacitor Recommendations for the PT5800 &
PT5810 Step-Down Regulator Series

Input Capacitor:

The recommended input capacitance is determined by a
700-mA ripple current rating and the following minimum
capacitance requirements.

· PT5800 =

820µF minimum capacitance

· PT5810 = 1000µF minimum capacitance

Ripple current and <100m

equivalent series resistance

(ESR) values are the major considerations, along with
temperature, when designing with different types of
capacitors. Tantalum capacitors have a recommended
minimum voltage rating of twice the maximum DC
voltage + AC ripple. This is necessary to ensure reliabil-
ity for input voltage bus applications

Output Capacitors

The ESR of the capacitors is less than 100m

. Electrolytic

capacitors have marginal ripple performance at frequen-
cies greater than 400kHz, but excellent low frequency
transient response. Above the ripple frequency ceramic
capacitors are necessary. Ceramic capacitors improve the
transient response and reduce any high frequency noise
components apparent during high current excursions.
Preferred low-ESR electrolytic capacitor part numbers
are identified in Table 3-1.

PT5800/5810 Series

Tantalum Capacitors (Optional Output Capacitors)

Tantalum type capacitors can be used for the output but
only the AVX TPS series, Sprague 593D/594/595 series,
or Kemet T495/T510 series. These capacitors are rec-
ommended over many other tantalum types due to their
higher rated surge, power dissipation, and ripple current
capability. As a caution the TAJ series by AVX is not
recommended. This series has considerably higher ESR,
reduced power dissipation, and lower ripple current
capability. The TAJ series is less reliable than the AVX
TPS series when determining power dissipation capa-
bility. Tantalum or Oscon® types are recommended for
applications where ambient temperatures fall below 0°C.

Capacitor Table

Table 2-1 identifies the characteristics of capacitors from a
number of vendors with acceptable ESR and ripple current
(rms) ratings. The number of capacitors required at both
the input and output buses is identified for each capacitor
type.

This is not an extensive capacitor list. Capacitors from other

vendors are available with comparable specifications. Those listed
are for guidance. The RMS ripple current rating and ESR
(Equivalent Series Resistance at 100kHz) are critical parameters
necessary to insure both optimum regulator performance and
long capacitor life.

)

(

)

(

)

(

)

(

)

(

)

(

1
1

1
1
1

)

(

2
3

1
1
1

)

(

2
2

1
1

)

(

2
2

1
1

(

)

3
3

1
1

(

)

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Application Notes

Using the Inhibit Control of the PT5800 & PT5810
Series of Step-Down ISRs

For applications requiring output voltage On/Off control,
the PT5800 & PT5810 series of ISRs incorporate an
inhibit function. This function can be used wherever there
is a requirement for the output voltage from the ISR to be
turned off. The On/Off function is provided by the Inhibit*
control (pin 2).

The ISR functions normally with pin 2 open-circuit,
providing a regulated output whenever a valid source
voltage is applied between V

(pins 57) and GND (pins

913). When a low-level

ground signal is applied to

pin 2, the regulator output is turned off

Figure 4-1 shows the typical application of the Inhibit*
function. Note the discrete transistor (Q

). The Inhibit*

control has its own internal pull-up to +V

potential. An

open-collector or open-drain device is recommended to
control this input

. The voltage thresholds are given in

Table 4-1.

Table 4-1; Inhibit Control Requirements

Parameter

Min

Typ

Max

Enable (VIH)

Vin 0.5V

Open

Disable (VIL)

0.2V

+0.8V

I IL

0.5 mA

Notes:
1. Use an open-collector device with a breakdown voltage

of at least 10V (preferably a discrete transistor) for the
Inhibit* input. A pull-up resistor is not necessary. To
disable the output voltage the control pin should be
pulled low to less than +0.8VDC.

2. When a ground signal is applied to the Inhibit* control

(pin 2) the module output is turned off (tri-state). The
output voltage decays to zero as the load impedance
discharges the output capacitors.

Figure 4-1

Turn-On Time:

In the circuit of Figure 4-1, turning Q

applies a low-voltage to the Inhibit* control (pin 2) and
disables the output of the regulator

. If Q

is then turned

off, the ISR executes a soft-start power up. Power up
consists of a short delay (approx. 2msec), followed by a
period in which the output voltage rises to its full regu-
lation voltage. The module produces a regulated output
voltage within 10msec. Figure 4-2 shows the typical rise
in both the output voltage and input current for a PT5812
(2.5V), following the turn-off of Q

. The turn off of Q

corresponds to the rise in the waveform, Q

. The

waveforms were measured with a 3.3VDC input voltage,
and 10-A load.

Figure 4-2

Vo (1V/Div)

Iin (5A/Div)

Q1 Vds (2V/Div)

HORIZ SCALE: 2ms/Div

PT5800 & PT5810 Series

PT5812

913

1417

5, 6, 7

1,000µF

OUT

330µF

1 =Inhibit

GND

OUT

Output Sense (+)

Output Sense ()

BSS138

Application Notes

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PT5800 & PT5810 Series

Adjusting the Output Voltage of the PT5800 &
PT5810 Step-Down Series of Regulators

Using Margin Up/ Margin Down

The Margin Up* (pin 4) and Margin Dn* (pin 3) control
inputs allow the output voltage to be easily adjusted by
up to ±5% of the nominal set-point voltage. To activate,
simply connect the appropriate control input to the Sense()
(pin 8), or the local starpoint ground. Either a logic level
MOSFET or a p-channel JFET is recommended for this
purpose. For further information see the related applica-
tion note on this feature.

Using the `V

Adjust' Control

For a more permanent and precise adjustment, use the
Vo Adjust control (pin 1). The V

Adjust control allows

adjustment in any increment by up to ±10% of the set-
point. The adjustment method requires the addition of a
single external resistor. Table 5-1 gives the allowable
adjustment range for each model of the series as V

(min)

and V

(max). The value of the external resistor can either

be calculated using the formulas given below, or simply
selected from the range of values provided in Table 5-2.
Refer to Figure 5-1 for the placement of the required
resistor. Use the resistor R

to adjust up, and the resistor

)

to adjust down.

Adjust Up: An increase in the output voltage is obtained
by adding a resistor R

, between V

Adjust (pin 1) and

Sense() (pin 8). See Figure 5-1.

Adjust Down: Add a resistor

)

, between V

Adjust (pin 1)

and Sense(+) (pin 18). See Figure 5-1.

Figure 5-1; V

Adjust Resistor Placement

Adjust Resistor Calculations

The values of R

[adjust up] and

)

[adjust down] can

also be calculated using the following formulas. Again, use
Figure 5-1for the placement of the required resistor;
either R

)

as appropriate.

· R

24.9

)

24.9

Where: V

= Original output voltage

= Adjusted output voltage

= The reference voltage in Table 5-1

= The resistance constant in Table 5-1

Table 5-1

ISR OUTPUT VOLTAGE ADJUSTMENT RANGE AND FORMULA PARAMETERS

Series Pt. No.

5.0V Bus

PT5801

PT5802

PT5803

PT5804

PT5805

PT5806

3.3V Bus

N/A

PT5812

PT5813

PT5814

PT5815

PT5816

Vo (nom)

3.3V

2.5V

1.8V

1.5V

1.2V

1.0V

Va (min)

2.6V

2.0V

1.52V

1.31V

1.1V

0.94V

Va (max)

3.63V

2.8V #

2.1V

1.82V

1.52V

1.32V

0.8V

Ro (k

)

10.2

10.7

10.2

9.76

10.0

10.2

# The PT5812 should not be adjusted higher than its nominal output voltage of 2.5V. See note 4.

Notes:
1. Use a 1% (or better) tolerance resistor in either the R

)

location. Place the resistor as close to the ISR as

possible.

2. Never connect capacitors from V

Adjust to either GND or

out

. Any capacitance added to the V

Adjust pin will affect

the stability of the ISR.

3. If the remote sense feature is not being used, the adjust

resistor

)

can be connected to V

out

, (pins 14-17) instead

of Sense (+).

PT5800/5810

913

1417

OUT

330µF

GND

OUT

Sense (+) [Note 3]

Sense ()

)

Adj Down

Adj

GND

Sense(+)

Sense()

OUT

Adjust Up

4. The PT5812 may not be adjusted higher than the

nominal output voltage of 2.5V. There is insufficient
input voltage between V

and V

out

to accommodate

an increase in the output voltage.

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Application Notes

continued

(req.d)

2.100

2.3k

2.050

7.7k

2.000

15.9k

1.950

29.5k

1.900

56.7k

1.850

138.0k

1.800

1.1k

1.750

(169.0)k

6.3k

1.700

(66.9)k

14.1k

1.650

(32.9)k

27.2k

1.600

(15.9)k

53.2k

1.550

(5.7)k

131.0k

1.500

1.8k

1.475

(239.0)k

4.2k

1.450

(102.0)k

7.1k

1.425

(56.4)k

10.7k

1.400

(33.7)k

15.1k

1.375

(20.0)k

20.8k

1.350

(10.9)k

28.4k

1.325

(4.4)k

39.1k

1.300

55.1k

2.3k

1.275

81.8k

4.8k

1.250

135.0k

7.7k

1.225

295.0k

11.4k

1.200

15.9k

1.175

(125.0)k

21.7k

1.150

(45.1)k

29.5k

1.125

(18.4)k

40.4k

1.100

(5.1)k

56.7k

1.075

83.9k

1.050

138.0k

1.025

302.0K

1.000

0.975

(46.5)k

0.950

(5.7)k

PT5800 & PT5810 Series

Table 5-2

ISR ADJUSTMENT RESISTOR VALUES

Series Pt. No.

5.0V Bus

PT5801

PT5802

PT5803

PT5804

PT5805

PT5806

3.3V Bus

N/A

PT5812

PT5813

PT5814

PT5815

PT5816

(nom)

3.3V

2.5V

1.8V

1.5V

1.2V

1.0V

(req.d)

3.60

2.3k

3.55

7.7k

3.50

15.9k

3.45

29.5k

3.40

56.7k

3.35

138.0k

3.30

3.25

(475.0)k

3.20

(220.0)k

3.15

(135.0)k

3.10

(92.4)k

3.05

(66.9)k

3.00

(49.9)k

2.95

(37.5)k

2.90

(28.6)k

2.85

(21.6)k

2.80

(15.9)k

3.6K

2.75

(11.3)k

9.3K

2.70

(7.4)k

17.9K

2.65

(4.1)k

32.2K

2.60

(1.3)k

60.7K

2.550

[Note 4

]

146.0K

2.500

2.450

(321.0)k

2.400

(146.0)k

2.350

(85.7)k

2.300

(55.3)k

2.250

(37.2)k

2.200

(25.0)k

2.150

(16.4)k

2.100

(9.9)k

2.050

(4.8)k

2.000

(0.8)k

= Black

(Blue)

Application Notes

For technical support and more information, see inside back cover or visit www.ti.com

Using the Margin Up/Down Controls on the
PT5800 & PT5810 Regulator Series

The PT5800 & PT5810 series of integrated switching
regulator modules incorporate Margin Up* (pin 4) and
Margin Dn* (pin 3) control inputs. These controls allow the
output voltage set point to be momentarily adjusted

either up or down, by a nominal 5%. This provides a
convenient method for dynamically testing the load
circuit's power supply voltage over its operating margin
or range. Note that the ±5% change is also applied to any
adjustment of the output voltage, if made, using the V

Adjust (pin 1).

The 5% adjustment is made by driving the appropriate
margin control input directly to the ground reference at
Sense(-) (pin 8)

. An low-leakage open-drain device, such as

a MOSFET or a p-channel JFET is recommended for this
purpose. Adjustments of less than 5% can also be accom-
modated by adding series resistors to the control inputs
(See Figure 6-1). The value of the resistor can be selected
from Table 6-1, or calculated using the following formula.

Resistor Value Calculation

To reduce the margin adjustment to something less than
5%, series padding resistors are required (See R

and

in Figure 6-1). For the same amount of adjustment,

the resistor value calculated for R

and R

will be the

same. The formulas is as follows.

499

99.8

Where

% = The desired amount of margin adjust in

percent.

Notes:
1. The Margin Up* and Margin Dn* controls were not

intended to be activated simultaneously. If they are
their affects on the output voltage may not completely
cancel, resulting in a slight shift in the output voltage
set point.

2. When possible use the Sense(-) (pin 8) as the ground

reference. This will produce a more accurate adjustment
of the output voltage at the load circuit terminals. GND
(pins 9-13) can be used if the Sense(-) pin is connected
to GND near the regulator.

out

+5V

GND

MargDn

O
A
D

Sense()

OUT

GND

PT5800

1417

913

5, 6, 7

OUT

GND

SNS(+)

SNS()

INHIBIT*

MARG

DN*

MARG

UP*

MargUp

Figure 6-1; Margin Up/Down Application Schematic

Table 6-1; Margin Up/Down Resistor Values

PADDING RESISTOR VALUES

% Adjust

/ R

0.0k

24.9k

66.5k

150.0k

397.0k

PT5800 & PT5810 Series

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