ST L6911B User Manual

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5 BIT PROGRAMMABLE POWER SUPPLY

CONTROLLERFOR PENTIUM II PROCESSOR

OPERATING SUPPLY VOLTAGE FROM 5V
TO 12V

TTL-COMPATIBLE 5BIT PROGRAMMABLE
OUTPUTFROM:

-1.3V TO 2.05VWITH0.05V BINARYSTEPS

-2.1V TO 3.5V WITH0.1V BINARYSTEPS
VOLTAGEMODEPWM CONTROL
EXCELLENT OUTPUT ACCURACY +/-1%

OVERLINE,ANDTEMPERATUREVARIA T IO NS
HIGH PRECISION INTERNAL REFERENCE

DIGITALLY TRIMMED
VERYFAST LOAD TRANSIENT0% TO 100%

DUTY CYCLE
POWERGOOD OUTPUT
OVERVOLTAGE PROTECTION
OVERCURRENT PROTECTION REALISED

USING THE MOSFET’sR
OPERATINGFREQUENCY FROM 50KHz TO

1MHz
MEETSINTEL PENTIUM II SPECIFICATION
DISABLEFUNCTION

APPLICATIONCIRCUIT

DSon

L6911B

SO20

Applications

POWER SUPPLY FOR ADVANCED MICRO­PROCESSORSUPPLIES

POWER SUPPLY FOR PENTIUM II INTEL
PROCESSORS

DESCRIPTION

The L6911B is a power supply controller specifi­cally designed to provide a high performance
DC/DC conversion for Pentium II Microproces­sors. A precise 5 bit digital to analog converter

April 1999

Vin 5V/12V

V

5V/12V

CC

VCC

OSC

OVP

VD0
VD1
VD2
VD3
VD4

SS

PGOOD 12

OCSET

18

20

19

4
5
6
7
8
3

2

BOOT

15

UGATE

14

Vo

13

PHASE

17

LGATE

16

PGND

11

GND

1

VSEN
VFB

10

COMP

9

1.3V to 3.5V

D98IN956B

1/7

L6911B

DESCRIPTION(continued)

(DAC) allows to adjust the output voltage from

1.3V to 2.05V with 0.05V binary steps and from

2.1V to 3.5V with 0.1V binary steps. The high pre­cision internal reference, digitally trimmed, as­sures the selected output voltage to within +/-1%.
Thanks to thewindow comparatorsystem,the de­vice provides excellent load transient perform­ance. The high peak current gate drive affords to

ABSOLUTEMAXIMUMRATINGS

Symbol Parameter Value Unit

V

CC

V

BOOT-VPHASE

VCCto PGND 15 V
Boot Voltage 15 V
Input, Output or I/O Voltage -0.3 to V

BLOCK DIAGRAM

V

12V

CC

have fast switching to the external power mos,
performing an high efficiency. The L6911B as­sures a fast protection against load overvoltage
and load overcurrent. An external SCR is trig­gered to crowbar the input supply in case of over­voltage. In case of output short circuit the soft
start capacitor is discharged and the system
works inhiccup mode.

+0.3 V

CC

Vin 5V

PGOOD

OVP

VD0
VD1
VD2
VD3
VD4

D98IN957A

SS

RT

D/A

VCC OCSET

MONITOR and
PROTECTION

OSC

+

­E/A

COMP

BOOT

UGATE

PHASE

LGATE

-

+

PWM

PGND

GND

VSEN

VFB

Vo

1.8V to 3.5V

THERMAL DATA

Symbol Parameter Value Unit

R

thj-amb

T

T

max

stg

Thermal Resistance Junction to Ambient 110 °C/W
Maximum Junction Temperature 150 °C
Storage Temperature Range -65 to 150 °C

RECOMMENDED OPERATINGCONDITION

Symbol Parameter Value Unit

2/7

V

CC

T

amb

T

J

VCCto PGND 5V±10%/12V±10% V
Ambient Temperature Range 0 to 70 °C
Junction Temperature Range 0 to 125 °C

PIN CONNECTION

L6911B

VSEN

OCSET

SS
VID0
VID1
VID2
VID3
VID4

COMP PGOOD

FB GND

2
3
4
5
6
7
8
9
10

D98IN958

20
19
18
17
16
15
14
13
12
11

RT1
OVP
VCC
LGATE
PGND
BOOT
UGATE
PHASE

PIN FUNCTIONS

N° Name Description

1 VSEN Connected to the output voltage is able to manage overvoltage conditions and the PGOOD

2 OCSET A resistor connected from this pin and the upper Mos Drain sets thecurrent limit protection.

3 SS The soft starttime is programmed connecting an external capacitor from this pin and GND.

4 - 8 VID0 - 4 Voltage Identification code pins. These input are open collector and TTL compatible. Are used

9 COMP This pin is connected to the error amplifier output and is used to compensate the voltage

10 FB This pin is connected to the error amplifier inverting inputand is used to compensate the

11 GND All internal voltage reference are referred to this pin.
12 PGOOD This pin is an open collectoroutput and is pulled low if the output voltage is not within±10%

13 PHASE This pin is connected to the source of the upper mosfet and provides the return pathfor the

14 UGATE High side gate driver output.
15 BOOT Bootstrap capacitor pin. Through this pin is supplied the high side driver and the upper mosfet.
16 PGND Power ground pin. This pin has to be connected closely to the low side mosfet source in order

17 LGATE This pin is the lower mosfet gate driver output.
18 VCC Device supply voltage. The operative supply voltage range is 4.5V to 12V.

19 OVP Over voltage protection. If the output voltage reach the 15% above the programmed voltage

signal.

The internal 200µA current generator sinks a currentfrom the drain through the external
resistor. The overcurrent threshold is due to the following equation:

I

⋅ R

ocs

I

=

P

ocs

Rdson

The internal current generator forces through the capacitor 10µA.This pin can be used to
disable the device forcing a voltage lower than 0.4V.

to program the output voltage as specified in Table 1 and to set the overvoltage and
powergood thresholds.

control feedback loop.

voltage control feedback loop.

of the programmed voltage. This pin is forced high if the ”11111” VID is set.

high side driver. This pin monitors the drop across the upper mosfet forthe current limit.

to reducethe noise injection into the device.

Do not connect V

to 12V if VCCis 5V.

IN

this pin is driven high and can be used to drive an external SCR that crowbar the supply
voltage.

3/7