OPERATING SUPPLY VOLTAGE FROM 5V
TO 12V
TTL-COMPATIBLE 5BIT PROGRAMMABLE
OUTPUT FROM:
-1.3V TO 2.05V WITH 0.05V BINARY STEPS
-2.1V TO 3.5V WITH 0.1V BINARY STEPS
VOLTAGE MODE PWM CONTROL
EXCELLENT OUTPUT ACCURACY +/-1%
OVERLINE, AND TEMPERATURE VARIATIONS
HIGH PRECISION INTERNAL REFERENCE
DIGITALLY TRIMMED
VERY FAST LOAD TRANSIENT 0% TO 100%
DUTY CYCLE
POWER GOOD OUTPUT
OVERVOLTAGE PROTECTION
OVERCURRENT PROTECTION REALISED
USING THE MOSFET's R
DSon
OPERATING FREQUENCY FROM 50KHz TO
1MHz
MEETS INTEL PENTIUM II SPECIFICATION
DISABLE FUNCTION
Applications
POWER SUPPLY FOR ADVANCED MICRO-
PROCESSOR SUPPLIES
POWER SUPPLY FOR PENTIUM II INTEL
PROCESSORS
DESCRIPTION
The L6911B is a power supply controller specifi-
cally designed to provide a high performance
DC/DC conversion for Pentium II Microproces-
sors. A precise 5 bit digital to analog converter
April 1999
10
PGND
PHASE
GND
VFB
LGATE
BOOT
UGATE
VCC
OCSET
11
16
17
13
14
15
V
CC
5V/12V
18
2
Vin 5V/12V
Vo
1.3V to 3.5V
4
5
6
7
8
1
PGOOD
12
19
3
20
VD0
VD1
VD2
VD3
VD4
COMP
VSEN
SS
OVP
OSC
9
D98IN956B
APPLICATION CIRCUIT
SO20
L6911B
5 BIT PROGRAMMABLE POWER SUPPLY
CONTROLLER FOR PENTIUM II PROCESSOR
1/7
(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 pre-
cision internal reference, digitally trimmed, as-
sures the selected output voltage to within +/-1%.
Thanks to the window comparator system, the de-
vice provides excellent load transient perform-
ance. The high peak current gate drive affords to
have fast switching to the external power mos,
performing an high efficiency. The L6911B as-
sures a fast protection against load overvoltage
and load overcurrent. An external SCR is trig-
gered to crowbar the input supply in case of over-
voltage. In case of output short circuit the soft
start capacitor is discharged and the system
works in hiccup mode.
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
V
CC
V
CC
to PGND
15
V
V
BOOT
-V
PHASE
Boot Voltage
15
V
Input, Output or I/O Voltage
-0.3 to V
CC
+0.3
V
THERMAL DATA
Symbol
Parameter
Value
Unit
R
th j-amb
Thermal Resistance Junction to Ambient
110
C/W
T
max
Maximum Junction Temperature
150
C
T
stg
Storage Temperature Range
-65 to 150
C
RECOMMENDED OPERATING CONDITION
Symbol
Parameter
Value
Unit
V
CC
V
CC
to PGND
5V
10%/12V
10%
V
T
amb
Ambient Temperature Range
0 to 70
C
T
J
Junction Temperature Range
0 to 125
C
DESCRIPTION (continued)
PGND
PHASE
GND
VFB
LGATE
BOOT
UGATE
VCC
OCSET
V
CC
12V
Vin 5V
Vo
1.8V to 3.5V
PGOOD
COMP
VSEN
SS
OVP
RT
VD0
VD1
VD2
VD3
VD4
MONITOR and
PROTECTION
OSC
D/A
E/A
PWM
+
-
-
+
D98IN957A
BLOCK DIAGRAM
L6911B
2/7
PIN FUNCTIONS
N
Name
Description
1
VSEN
Connected to the output voltage is able to manage overvoltage conditions and the PGOOD
signal.
2
OCSET
A resistor connected from this pin and the upper Mos Drain sets the current limit protection.
The internal 200
A current generator sinks a current from the drain through the external
resistor. The overcurrent threshold is due to the following equation:
I
P
=
I
ocs
R
ocs
Rdson
3
SS
The soft start time is programmed connecting an external capacitor from this pin and GND.
The internal current generator forces through the capacitor 10
A. This pin can be used to
disable the device forcing a voltage lower than 0.4V.
4 - 8
VID0 - 4
Voltage Identification code pins. These input are open collector and TTL compatible. Are used
to program the output voltage as specified in Table 1 and to set the overvoltage and
powergood thresholds.
9
COMP
This pin is connected to the error amplifier output and is used to compensate the voltage
control feedback loop.
10
FB
This pin is connected to the error amplifier inverting input and is used to compensate the
voltage control feedback loop.
11
GND
All internal voltage reference are referred to this pin.
12
PGOOD
This pin is an open collector output and is pulled low if the output voltage is not within
10%
of the programmed voltage. This pin is forced high if the "11111" VID is set.
13
PHASE
This pin is connected to the source of the upper mosfet and provides the return path for the
high side driver. This pin monitors the drop across the upper mosfet for the current limit.
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
to reduce the noise injection into the device.
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.
Do not connect V
IN
to 12V if V
CC
is 5V.
19
OVP
Over voltage protection. If the output voltage reach the 15% above the programmed voltage
this pin is driven high and can be used to drive an external SCR that crowbar the supply
voltage.
VSEN
OCSET
SS
VID0
VID1
VID3
VID2
VID4
COMP
PGOOD
PHASE
UGATE
PGND
BOOT
LGATE
VCC
OVP
RT
1
3
2
4
5
6
7
8
9
18
17
16
15
14
12
13
11
19
10
20
FB
GND
D98IN958
PIN CONNECTION
L6911B
3/7
ELECTRICAL CHARACTERISTICS
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
VCC SUPPLY CURRENT
I
CC
Supply current
UGATE and LGATE open
-
5
-
mA
POWER-ON
Rising V
CC
Threshold
VOCSET = 4.5V
-
-
4.6
V
Falling V
CC
Threshold
VOCSET = 4.5V
3.6
-
-
V
Rising VOCSET Threshold
-
1.26
-
V
OSCILLATOR
Free Running Frequency
RT = open
185
200
215
kHz
Total Variation
R
T
to GND >6k
,
R
T
to V
CC
= 12V > 200k
-15
-
15
%
V
osc
Ramp Amplitude
RT = open
-
1.9
-
V
REFERENCE and DAC
DACOUT voltage Accuracy
VID0, VID1, VID2, VID3 see
Table1
-1
-
1
%
ERROR AMPLIFIER
DC Gain
-
88
-
dB
GBW
Gain-Bandwidth Product
-
15
-
MHz
SR
Slew Rate
COMP = 10pF
-
10
-
V/
s
GATE DRIVERS
I
UGATE
Upper Gate Source
V
BOOT
- Vphase = 12V,
V
UGATE
= 6V
0.6
1
-
A
R
UGATE
Upper Gate Sink
I
LGATE
= 0.3A
-
1.5
3
I
LGATE
Lower Gate Source
V
CC
= 12V, V
LGATE
= 6V
1.2
2
-
A
R
LGATE
Lower Gate Sink
I
LGATE
= 0.3A
-
1
2
PROTECTION
Overvoltage Trip
(V
SEN
/DACOUT)
-
115
120
%
I
OCSET
OCSET Current Source
V
OCSET
= 4.5VDC
170
200
230
A
I
OVP
OVP Sourcing Current
V
SEN
= 5.5V, V
OVP
= 0V
60
mA
I
SS
Soft Start Current
10
A
N
Name
Description
20
RT
Oscillator Switching frequency pin. Connecting an external resistor from this pin to ground the
switching frequency is increased according to the equation:
f
S
=
200kHz
+
5
10
6
R
T
(
K
)
Connecting the resistor from this pin and the Vcc the Switching frequency is reduced
according to the equation:
f
S
=
200kHz
-
4
10
7
R
T
(
K
)
If the pin is not connected the switching frequency is 200kHz.
PIN FUNCTION (continued)
L6911B
4/7
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
Upper Threshold
(V
SEN
/DACOUT)
V
SEN
Rising
106
-
111
%
Upper Threshold
(V
SEN
/DACOUT)
V
SEN
Rising
89
-
94
%
Hysteresis
(V
SEN
/DACOUT)
Upper and Lower Threshold
-
2
-
%
V
PGOOD
PGOOD Voltage Low
I
PGOOD
= -5mA
-
0.5
-
V
ELECTRICAL CHARACTERISTICS (continued)
Table 1.
VID4
VID3
VID2
VID1
VID0
OUTPUT VOLTAGE (V)
0
1
1
1
1
1.3
0
1
1
1
0
1.35
0
1
1
0
1
1.4
0
1
1
0
0
1.45
0
1
0
1
1
1.5
0
1
0
1
0
1.55
0
1
0
0
1
1.6
0
1
0
0
0
1.65
0
0
1
1
1
1.7
0
0
1
1
0
1.75
0
0
1
0
1
1.8
0
0
1
0
0
1.85
0
0
0
1
1
1.9
0
0
0
1
0
1.95
0
0
0
0
1
2
0
0
0
0
0
2.05
1
1
1
1
1
0
1
1
1
1
0
2.1
1
1
1
0
1
2.2
1
1
1
0
0
2.3
1
1
0
1
1
2.4
1
1
0
1
0
2.5
1
1
0
0
1
2.6
1
1
0
0
0
2.7
1
0
1
1
1
2.8
1
0
1
1
0
2.9
1
0
1
0
1
3
1
0
1
0
0
3.1
1
0
0
1
1
3.2
1
0
0
1
0
3.3
1
0
0
0
1
3.4
1
0
0
0
0
3.5
L6911B
5/7
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