PT8121 [TI]

30-A 12-V Input Programmable Integrated Switching Regulator; 30 -A 12 - V输入可编程集成开关稳压器


型号：	PT8121
厂家：	TEXAS INSTRUMENTS
描述：	30-A 12-V Input Programmable Integrated Switching Regulator 30 -A 12 - V输入可编程集成开关稳压器稳压器开关
文件：	总10页 (文件大小：185K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

PT8120 Series

30-A 12-V Input Programmable

Integrated Switching Regulator

SLTS158B

(Revised 6/6/2002)

Features

• Single Device: 30ADC

• +12V-Input

• High Efficiency: 92% @3.3V

• Programmable Output:

(VRM Compatible 5-bit Codes)

• Thermal Shutdown

• Standby On/Off Control

• Space-Saving Package

• Solderable Copper Case

• Multiphase Topology

• Output Remote Sense

• Over-Current Protection

Description

Ordering Information

The PT8120 Excalibur™ power

modules are a family of high-output,

high-efficiency, fully integrated

switching regulators (ISRs), housed

in a solderable 31-pin space-saving

copper package. These modules

operate from a nominal input voltage

of +12V to provide up to 30A of

output current at output voltages as

low as 0.8V. The output voltage is

programmable via a 5-bit input code.

The PT8120 family incorporates

a state-of-the-art, 2-phase, multiple

power path topology. This extends

the output current range while pro-

viding superior transient response

and input current ripple performance.

The PT8120 family is designed

to power high-end computing and

signal processing applications, all of

which demand high output currents

at low supply voltages.

The modules have a number of

features to facilitate system integra-

tion. These include over-current

protection, thermal shutdown, an

on/off standby control, and an output

remote sense to compensate for

voltage drop between the regulator

and the load. In addition, the volt-

age programming codes for the

PT8121, PT8122, & PT8124 are

compatible with Intel’s® VRM

specifications.

PT 8121r = 1.3V

to 3.5V

PT 8122r = 1.075V to 1.85V

PT 8123r = 0.8V

to 1.575V

PT 8124r = 1.05V to 1.825V

PT 8125r = 4.5V to 7.6V

PT Series Suffix

(PT1234x)

Case/Pin

Configuration

O rder

Suffix

Package

Code

Vertical

Horizontal

SMD

(EKH)

(EKF)

(EKG)

(Reference the applicable package code drawing for

the dimensions and PC board layout)

PT812x Standard Application (See page 4 for PT8124 application schematic)

PROGRAMMING PINS

VID0

VID1

VID2

VID3

VID4

REMOTE SENSE

VID

Common

L_in

V_OUT

PT8120 Series

12–16

23–30

V_IN

(Except PT8124)

1µH

17–22

C_IN

C_OUT

GND

STBY*

C_in= Required 1500µF electrolytic

C_out= Required 660µF low ESR OS-Con®, or

1,200µF aluminum electrolytic

L_in= Optional 1µH input choke

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

PT8120 Series

30-A 12-V Input Programmable

Integrated Switching Regulator

†

Pin-Out Information (Except PT8124

)

Pin Function

12 V_in

Pin Function

22 GND

23 V_out

VID 0

VID 1

13 V_in

VID 2

14 V_in

24 V_out

VID 3

15 V_in

25 V_out

VID 4

16 V_in

26 V_out

STBY *

17 GND

18 GND

19 GND

20 GND

21 GND

27 V_out

Do Not Connect

28 V_out

29 V_out

30 V_out

10 Do Not Connect

11 VID Common

31 Remote Sense

*For STBY pin:

† See page 4 for PT8124 pin-out

Open

=Output Enabled

Ground =Output Disabled

Output Voltage Programming Information (Except PT8124)

PT8122

(VRM 9.0)

PT8123

(Custom Code)

PT8125

(Custom Code)

PT8121

(VRM 8.3/8.4)

VID 4=1

Vout

VID 4=0

Vout

VID 4=1

Vout

VID 4=0

Vout

VID 4=1

Vout

VID 4=0

Vout

VID 4=1

Vout

VID 4=0

VID 3 VID 2 VID 1 VID 0

Vout

6.1V

6.2V

6.3V

6.4V

6.5V

6.6V

6.7V

6.8V

6.9V

7.0V

7.1V

7.2V

7.3V

7.4V

7.5V

7.6V

1.075V

1.100V

1.125V

1.150V

1.175V

1.200V

1.225V

1.250V

1.275V

1.300V

1.325V

1.350V

1.375V

1.400V

1.425V

1.450V

1.475V

0.800V

0.825V

0.850V

0.875V

0.900V

0.925V

0.950V

0.975V

1.000V

1.025V

1.050V

1.075V

1.100V

1.125V

1.150V

1.175V

1.200V

4.5V

2.00V

2.10V

2.20V

2.30V

2.40V

2.50V

2.60V

2.70V

2.80V

2.90V

3.00V

3.10V

3.20V

3.30V

3.40V

3.50V

1.30V

1.35V

1.40V

1.45V

1.50V

1.55V

1.60V

1.65V

1.70V

1.75V

1.80V

1.85V

1.90V

1.95V

2.00V

2.05V

1.500V

1.525V

1.550V

1.575V

1.600V

1.625V

1.650V

1.675V

1.700V

1.725V

1.750V

1.775V

1.800V

1.825V

1.850V

1.225V

1.250V

1.275V

1.300V

1.325V

1.350V

1.375V

1.400V

1.425V

1.450V

1.475V

1.500V

1.525V

1.550V

1.575V

4.6V

4.7V

4.8V

4.9V

5.0V

5.1V

5.2V

5.3V

5.4V

5.5V

5.6V

5.7V

5.8V

5.9V

6.0V

Notes:

i) Logic 0 = Connect to VID Common

ii) Logic 1 = Open circuit (no pull-up resistors)

iii) VID3 and VID4 may not be changed while the unit is operating.

iv) See page 4 for PT8124 (VRM 8.5) programming information.

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

PT8120 Series

30-A 12-V Input Programmable

Integrated Switching Regulator

PT8121 /2 /3 /5 Specifications (Unless otherwise stated T_a=25°C, C_in=1,500µF, C_out=660µF, V_in=12V, & I_o= I_omax )

PT8121 /2 /3 /5 Only

Characteristics

Symbols

Conditions

Min

Typ

Max

Units

(1)

Output Current

I_o

Natural convection or

_o≤3.5V 0.1

_o≥4.5V 0.1

—

60°C with 200LFM airflow

Input Voltage Range

Set-Point Voltage Tolerance

Line Regulation

V_in

Over I_oRange

Over V_orange

Over V_inrange

Over I_orange

10.8

—

13.2

V_otol

%V_o

∆Reg_line

∆Reg_load

∆Reg_temp

∆V_otot

—

0.5

—

Load Regulation

—

Temperature Variation

Total Output Voltage Variation

–40°C ≤T_a≤85°C

—

Includes set-point, line load,

–40°C ≤T_a≤ 85°C

—

Efficiency

I_o=15A

V_o=5.0V

V_o=3.3V

V_o=2.5V

V_o=1.8V

V_o=1.5V

Vo =1.2V

—

_o=I_omax

V_o=5.0V

V_o=3.3V

V_o=2.5V

V_o=1.8V

V_o=1.5V

V_o=1.2V

—

V_oRipple (pk-pk)

V_r

20MHz bandwidth

—

µSec

Transient Response

t_tr

1A/µs load step, 50% to 100% Iomax

V_oover/undershoot

∆V_tr

I_TRIP

100

Over-Current Threshold

Switching Frequency

Reset followed by auto-recovery

_o≥4.5V

_o≤3.5V

—

ƒ_s

Over load range

300

350

400

kHz

Standby Control (pin 6)

Input High Voltage

Input Low Voltage

Referenced to GND (pins 17–22)

(2)

—

-0.2

—

Open

0.8

V_IH

V_IL

Input Low Current

I_IL

Pin 6 to GND

—

0.5

—

µF

Standby Input Current

External Output Capacitance

External Input Capacitance

Operating Temperature Range

Storage Temperature

I_instandby

Pin 6 to GND

—

(3)

(4)

C_out

C_in

T_a

See PT812x application schematic

Over V_inRange

660

1,500

–40

-40

30,000

—

µF

(5)

+85

°C

T_s

—

+125

Mechanical Shock

Per Mil-STD-883D, Method 2002.3

1 msec, Half Sine, mounted to a fixture

—

500

—

G’s

Mechanical Vibration

Mil-STD-883D, Method 2007.2

20-2000 Hz, soldered in PCB

(6)

—

G’s

Weight

—

Vertical/Horizontal

grams

Flammability

Materials meet UL 94V-0

Notes: (1) ISR-will operate down to no load with reduced specifications.

(2) The Standby input (pin 6) has an internal pull-up. If it is left open-circuit the PT812x will operate when input power is applied. A low-leakage

MOSFET is recommended to control this input. The open-circuit voltage is nominally 5V. See application notes for interface considerations.

(3) The PT8120 regulators require a minimum of 660µF, low ESR ouput capacitance (1,200µF for standard aluminum electrolytic) for proper operation.

(4) For operation below 0°C, C_outmust have stable characteristics. Use either low ESR tantalum or Oscon® capacitors.

(5) See safe Operating Area curves or consult factory for the appropriate derating.

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

Input Filter: An input filter inductor is optional for most applications. The inductor must be rated to handle the projected input current. A rating of 10ADC for

V_out≤3.3V, and 15ADC for V_out≥4.5V is recommended. The input capacitance must be rated for a minimum of 1.6Arms of ripple current. For transient or dynamic

load applications, additional capacitance may be required. For more information consult the application note on capacitor selection.

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

PT8120 Series

30-A 12-V Input Programmable

Integrated Switching Regulator

PT8124 Voltage Programming Information

PT8124 Pin-Out Information

(VRM 8.5)

Pin Function

VID 25mV=0

Vout

VID 25mV=1

VID 25mV

VID 0

17 GND

18 GND

19 GND

20 GND

21 GND

22 GND

23 V_out

VID 3 VID 2 VID 1 VID 0

Vout

1.300V

1.325V

1.375V

1.425V

1.475V

1.525V

1.575V

1.625V

1.675V

1.725V

1.775V

1.825V

1.075V

1.125V

1.175V

1.225V

1.275V

VID 1

1.350V

1.400V

1.450V

1.500V

1.550V

1.600V

1.650V

1.700V

1.750V

1.800V

1.050V

1.100V

1.150V

1.200V

1.250V

VID 2

VID 3

STBY

Do Not Connect

24 V_out

25 V_out

10 Do Not Connect

11 VID Common

12 V_in

26 V_out

27 V_out

28 V_out

13 V_in

29 V_out

14 V_in

30 V_out

15 V_in

31 Remote Sense

16 V_in

*For STBY pin:

Notes:

Open

=Output Enabled

i) Logic 0 = Connect to VID Common

ii) Logic 1 = Open circuit (no pull-up resistors)

Ground =Output Disabled

iii) VID2 and VID3 may not be changed while the unit is operating.

PT8124 Standard Application

PROGRAMMING PINS

VID 25mV

VID 0

VID 1

VID 2

VID 3

REMOTE SENSE

VID

Common

L_in

V_OUT

PT8124

(Only)

12–16

23–30

V_IN

1µH

17–22

C_IN

C_OUT

GND

STBY*

C_in= Required 1500µF electrolytic

C_out= Required 660µF low ESR OS-Con®, or

1,200µF aluminum electrolytic

L_in= Optional 1µH input choke

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

PT8120 Series

30-A 12-V Input Programmable

Integrated Switching Regulator

PT8124 Specifications (Unless otherwise stated T_a=25°C, C_in=1,500µF, C_out=660µF, V_in=12V, & I_o= I_omax )

PT8124 Only

Characteristics

Symbols

Conditions

Min

Typ

Max

Units

Output Current

I_o

Natural convection or

(1)

0.1

—

60°C with 200LFM airflow

Input Voltage Range

V_in

Over I_oRange

10.8

—

13.2

Set-Point Voltage Tolerance

Line Regulation

V_otol

Over V_orange, I_o=0.5A

Over V_inrange

∆Reg_line

∆Reg_load

∆Reg_temp

∆V_otot

—

Load Regulation (Droop)

Temperature Variation

Total Output Voltage Variation

Over I_orange

—

mV/A

%V_o

–40°C ≤T_a≤85°C, , I_o=0.5A

—

0.5

Includes set-point, line, load

(2)

—

–40°C ≤T_a≤ 85°C

Efficiency

I_o=15A

V_o=1.8V

V_o=1.5V

V_o=1.2V

—

_o=I_omax

V_o=1.8V

V_o=1.5V

V_o=1.2V

—

V_oRipple (pk-pk)

V_r

20MHz bandwidth

—

µSec

Transient Response

t_tr

1A/µs load step, 50% to 100% Iomax

V_oover/undershoot

—

∆V_tr

I_TRIP

ƒ_s

—

Over-Current Threshold

Switching Frequency

Reset followed by auto-recovery

Over load range

—

300

350

400

kHz

Standby Control (pin 6)

Input High Voltage

Input Low Voltage

Referenced to GND (pins 17–22)

(3)

—

-0.2

—

Open

0.8

—

V_IH

V_IL

I_IL

—

Input Low Current

Pin 6 to GND

0.5

µF

Standby Input Current

External Output Capacitance

External Input Capacitance

Operating Temperature Range

Storage Temperature

I_instandby

Pin 6 to GND

—

(4)

(5)

C_out

C_in

T_a

See PT8124 application schematic

Over V_inRange

660

1,500

–40

-40

30,000

—

µF

+85 ⁽⁶⁾

+125

°C

T_s

—

Mechanical Shock

Per Mil-STD-883D, Method 2002.3

1 msec, Half Sine, mounted to a fixture

—

500

—

G’s

Mechanical Vibration

Mil-STD-883D, Method 2007.2

20-2000 Hz, soldered in PCB

(7)

—

G’s

Weight

—

Vertical/Horizontal

grams

Flammability

Materials meet UL 94V-0

Notes: (1) ISR-will operate down to no load with reduced specifications.

(2) Total output voltage variation includes load regulation droop, which is required for compliance with specification VRM 8.5-4

(3) The Standby input (pin 6) has an internal pull-up. If it is left open-circuit the PT812x will operate when input power is applied. A low-leakage

MOSFET is recommended to control this input. The open-circuit voltage is nominally 5V. See application notes for interface considerations.

(4) The PT8120 regulators require a minimum of 660µF, low ESR ouput capacitance (1,200µF for standard aluminum electrolytic) for proper operation.

(5) For operation below 0°C, C_outmust have stable characteristics. Use either low ESR tantalum or Oscon® capacitors.

(6) See safe Operating Area curves or consult factory for the appropriate derating.

(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.

Input Filter: An input filter inductor is optional for most applications. The inductor must be rated to handle the projected input current. A rating of 10ADC for

V_out≤3.3V, and 15ADC for V_out≥4.5V is recommended. The input capacitance must be rated for a minimum of 1.6Arms of ripple current. For transient or dynamic

load applications, additional capacitance may be required. For more information consult the application note on capacitor selection.

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

PT8120 Series

30-A 12-V Input Programmable

Integrated Switching Regulator

Characteristic Data; V_in=12V (See Note A)

Safe Operating Area; V_in=12V (See Note B)

Efficiency vs Output Current

PT8120 Series, V_out=5V

100

V_OUT

Airflow

3.3V

2.5V

400LFM

200LFM

120LFM

60LFM

1.8V

1.5V

1.2V

1.0V

Nat conv

0.8V

Iout (A)

Output Ripple vs Output Current

PT8120 Series, V_out=3.3V

Airflow

V_OUT

Nat conv

60LFM

0.8V

120LFM

200LFM

400LFM

3.3V

1.5V

Iout (A)

Power Dissipation vs Output Current

PT8120 Series, V_out=1.5V

Airflow

V_OUT

400LFM

200LFM

120LFM

60LFM

3.3V

1.5V

0.8V

Nat conv

Iout (A)

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

Note B: SOA curves represent the conditions at which internal components are at or below the manufacturer’s maximum operating temperatures

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

Application Notes

PT8120 Series & PT8139

Capacitor Recommendations for the

PT8120 Series of Programmable ISRs

Tantalum Characteristics

Tantalum capacitors are recommended on the output bus

but only AVX TPS Series, Sprague 593D/594/595 Series,

or Kemet T495/T510,520 Series. These capacitors are

recommended over other types due to their higher surge

current, excellent power dissipation and ripple current

ratings. As a caution, the TAJ Series by AVX is not rec-

ommended. This series exhibits considerably higher ESR,

reduced power dissipation and lower ripple current capa-

bility. The TAJ Series is also less reliable compared to the

TPS series when determining power dissipation capability.

Input Capacitors

The recommended input capacitor(s) is determined by

1.6 Arms minimum ripple current rating and 1,500µF

minimum capacitance. Ripple current and Equivalent

Series Resistance (ESR) values are the major considerations

along with temperature when selecting the proper capaci-

tor. The tantalum capacitors listed below cannot be used

on the input bus since they are not rated for 12V operation.

Capacitor Table

Output Capacitors

Table 1 identifies the characteristics of capacitors from a

number of vendors with acceptable ESR and ripple current

(rms) ratings. The suggested minimum quantities per

regulator for both the input and output buses are identified.

The minimum required output capacitance is 660µF

(organic/polymer), or 1,200 (aluminum electrolytic) with

a maximum ESR less than or equal to 50mΩ. Failure to

observe this requirement may lead to regulator instabil-

ity or oscillation. Electrolytic capacitors have poor ripple

performance at frequencies greater than 400kHz, but

excellent low frequency transient response. Above the

ripple frequency ceramic decoupling capacitors are nec-

essary to improve the transient response and reduce any

microprocessor high frequency noise components apparent

during higher current excursions. Preferred low ESR type

capacitor part numbers are identified in the Table 1 below.

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 the

critical parameters are necessary to insure both optimum

regulator performance and long capacitor life.

Table 1 Capacitors Characteristic Data

Capacitor Vendor/

Series

Capacitor Characteristics

Quantity

Working

Voltage

Value(µF)

(ESR) Equivalent

Series Resistance

105°C Maximum

Ripple

Physical

Size(mm)

Input

Bus

Output

Bus

Vendor Part Number

Current(Irms)

Panasonic

FC (Radial)

35V

25V

1500

0.028Ω

0.029Ω

2490mA

2205mA

18× 20

16× 20

EEUFC1V152S

EEUFC1E152S

16V

25V

16V

4700

2200

0.033Ω

0.028Ω

0.038Ω

2060mA

2490mA

2000mA

18×16.5

18×21.5

18×16.5

EEVFK1C472M

EEVFC1E222N

EEVFC1C222N

FC/FK (Surface Mount)

United Chemi-con

LXZ Series

35V

25V

16V

1800

2700

0.028Ω

0.029Ω

2490mA

2210mA

18× 20

16×20

16× 20

LXZ35VB182M18X20LL

LXZ25VB182M16X20LL

LXZ16VB272M16X20LL

Nichicon

PW Series

25V

1000

1800

0.038÷2Ω

0.029Ω

3200mA

2205mA

12.5x20

16x20

UPW1E102MHH

UPW1E182MHH6

PM Series

25V

1500

0.034Ω

1770mA

16×20

UPM1E152MHH6

Os-con:( Organic)

SV (Surface Mount)

10V

330

0.025Ω

0.020Ω

3500mA

3800mA

10×10.5

10.3×10.3

N/R(1)

10SS330M (V_o<6V)

10SV330 (V_o<6V)

AVX Tantalum

TPS (Surface Mount)

10V

330

0.1Ω÷2 =0.05Ω

0.06Ω÷2 =0.03Ω

>2500mA

>3000mA

7.3L

×5.7W

×4.1H

N/R(1)

TPSE337M010R0100 (V_o<5V)

TPSV337M010R0060( V_o<5V)

Kemet

10V

330

0.040÷2Ω

1800mA

>1800mA

4.3W

×7.3L

×4.0H

N/R(1)

T520X337M010AS (V_o<6V)

T520D330M006AS (V_o<4V)

Polymer/Tantalum

T520Series

(Surface Mount)

Sprague Tantalum

594D Series

(Surface Mount)

10V

330

0.045÷2Ω

2360mA

7.2L

×6W

×4.1H

N/R(1)

594D337X0010R2T(V_o<5V)

Note: (N/R -Not recommended) The 10V-rated tantalum capacitors cannot be used on the input bus.

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

Application Notes

PT8120 Series & PT8139

Using the On/Off Standby Function of the

PT8120 Series of Programmable ISRs

The PT8120 series of programmable ISRs incorporates

an On/Off Standby function. This feature may be used

to turn the regulated output of the module off while input

voltage is applied. This places the module in “standby”

mode. The standby control may be used for power-up

sequencing, or wherever there is a requirement to control

the module’s output status from another circuit.

2. In the standby mode the output of the regulator is tri-

state, and the output voltage falls at the rate that the

load circuit discharges the output filter capacitors.

3. When the ground signal to the Standby pin is

removed, the regulator output initiates a soft-start

cycle by first asserting a low impedance to ground. If

an external voltage is applied to the output bus, it will

sink current and possibly over-stress the part.

The Standby function is provided by the STBY* control,

pin 6. If pin 6 is left open-circuit the regulator operates

normally, providing a regulated output when a valid sup-

ply voltage is applied to V_in(pins 10-16) with respect to

Turn-On Time

Turning Q₁in Figure 1 off, removes the low-voltage

signal at pin 6. After approximately 5-ms the regulator

output rises and reaches full regulation within 40ms.

Fig. 2 shows the typical waveforms of a PT8121 following

the prompt turn-off of Q₁. The turn-off of Q₁corresponds

to the rise in V_stby. The output voltage was set to 3.3V,

and the waveforms were measured with a 12V input source,

and 18A resistive load.

GND (pins 17-22). Connecting pin 6 to ground places

the regulator in standby mode , and reduces the input

current to typically 35mA. Applying a ground signal to

pin 6 prior to power-up, will inhibit the output during

the period that input power is applied. When the ground

signal to pin 6 is removed, the regulator initiates a soft-

start to re-establish the set output voltage. To ensure

that the regulator output is properly enabled, the STBY*

control pin must be open circuit.

Table 1 Standby Control Requirements ²

Figure 2

Parameter

V_IH

Min

—

Typ

Max

Open Cct.

0.8V

V_IL

–0.2V

—

Vo (1V/Div)

I_STBY

–0.5mA

Notes:

1. The standby on a PT8120 series regulators must be

controlled with an open-collector (or open-drain)

transistor (See fig. 1). Do Not use a pull-up resistor.

Table 1 gives the STBY* pin parameters. The control

pin has an open-circuit voltage of 5Vdc. To shut the

regulator output off, the control pin must be “pulled” to

less than 0.8Vdc with a low-impedance sink to ground.

Iin (5A/Div)

Vstby (5V/Div)

HORIZ SCALE: 5ms/Div

Figure 1

V_OSENSE

VID

Common

VID4 – VID0

Sense

L_in

V_IN

V_O=3.3V

12–16

23–30

V_IN

V_OUT

PT8121

1µH

STBY

GND

17–22

C_IN

C_OUT

BSS138

1 =Off

GND

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

Application Notes

PT8120 Series & PT8139

Pin-Coded Output Voltage Programming of the

30-A Rated PT8120 Series Regulators

4. If active devices are used to ground the voltage control

pins, low-level open drain MOSFETs should be used over

bipolar transistors. The inherent V_ce(sat) in bipolar devices

introduces errors in the device’s internal voltage control

circuit. Discrete transistors such as the BSS138, 2N7002,

IRLML2402, are examples of appropriate devices.

The PT8120 series of Excalibur® ISRs incorporate a

pin-coded output voltage control. These regulators must

be programmed to a specific output voltage from a pre-

set range defined by the regulator model. Programming

is achieved by selectively connecting the control inputs,

“VID0–VID4” (pins 1–5), to the “VID Common” (pin 11).

The programming code and voltage range for each model

is defined in the data sheet. Refer to the PT8120 Series

data sheet for more information. The program codes for

the PT8121, PT8122, and PT8124 models are also com-

patible with some of the “Voltage ID” codes defined by

Intel’s® VRM specifications. Figure 1 shows the pin-strap

connections for selecting the desired output voltage from

the program code range.

Active Voltage Programming:

Special precautions should be taken when making changes

to the voltage control progam code while the output is

active. It is recommended that the ISR be powered down

or held placed in standby. Changes made to the program

code while V_outis active induces high current transients

through the device. This is the result of the electrolytic

output capacitors being either charged or discharged to the

new output voltage set-point. The transient current can be

minimized by making only incremental changes to the

binary code, i.e. one LSB at a time. A minimum of 100µs

settling time between each program state is also recom-

mended. Making non-incremental changes to VID3 and

VID4 with the output enabled is discouraged. The tran-

sients induced may activate the module’s over-current

protection. If the program code cannot be asserted prior

to power-up, pull pin 6, STBY*, to GND during the

period that the input voltage is applied. The release of

pin 6 will then to allow the device to initiate a soft-start

power-up to the program voltage.

Notes:

1. The programming convention is as follows:-

Logic 0:

Logic 1:

Connect to pin 11 (VID Common).

Open circuit/open drain (See notes 2, & 4)

2. Do not connect pull-up resistors to the voltage

programming pins.

3. To minimize output voltage error, use pin 11 (VID

Common) as the logic “0” reference. If the regulator is

used to power a VRM compatible microprocessor this

may not be practical. In this case connect pin 11 to pins

17–22, or the ground plane close to the regulator.

Figure 1

VID0

VID1

VID2

VID3

VID4

V_OSENSE

VID4 – VID0 Sense

VID

Common

L_in

V_IN

V_O=2.5V

12–16

23–30

V_IN

V_OUT

PT8121

1µH

STBY

GND

17–22

C_IN

C_OUT

GND

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

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PT8121 [TI]

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