L4992 Datasheet PDF - STMicroelectronics


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L4992
STMicroelectronics

Part Number L4992
Description TRIPLE OUTPUT POWER SUPPLY CONTROLLER
Page 26 Pages

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® L4992
TRIPLE OUTPUT POWER SUPPLY CONTROLLER
DUAL PWM BUCK CONTROLLERS (3.3V
and 5.1V)
12V/120mA LINEAR REGULATOR
DUAL SYNCH RECTIFIERS DRIVERS
96% EFFICIENCY ACHIEVABLE
50µA (@ 12V) STAND BY CONSUMPTION
5.5V TO 25V SUPPLY VOLTAGE
EXCELLENT LOAD TRANSIENT RESPONSE
DISABLE PULSE SKIPPING FUNCTION
POWER MANAGEMENT:
- UNDER AND OVERVOLTAGE OUTPUT
DETECTION
- POWER GOOD SIGNAL
- SEPARATED DISABLE
THERMAL SHUTDOWN
PACKAGE: TQFP32
APPLICATION
NOTEBOOK AND SUBNOTEBOOK COM-
PUTERS
PEN TOP AND PORTABLE EQUIPMENT
COMMUNICATING COMPUTERS
DESCRIPTION
The L4992 is a sophisticated dual PWM step-
down controller and power monitor intended for
Notebook computer and/or battery powered
equipment. The device produces regulated
+3.3V, +5.1V and 12V supplies for use in portable
SYSTEM BLOCK DIAGRAM
TQFP32
ORDERING NUMBER: L4992
and PCMCIA applications.
The internal architecture allows to operate with
minimum external components count. A very high
switching frequency (200/300 KHz or externally
synchronizable) optimizes their physical dimen-
sions.
Synchronous rectification and pulse skipping
mode for the buck sections optimise the overall
efficiency over a wide load current range (96% ef-
ficiency @1A/5.1V and 93% efficiency @
0.05A/5.1V.
The two high performance PWM controllers for
+3.3V and +5.1V lines are monitored for overvol-
tage, undervoltage and overcurrent conditions.
On detection of a fault, a POWER GOOD signal
is generated and a specific shutdown procedure
takes place to prevent physical damage and data
corruption.
A disable function allows to manage the output
power sections separately, optimising the quies-
cent consumption of the IC in stand-by conditions.
5.5V
to
25V
SYNC
L4992
D96IN429A
June 2000
POWER
MANAGEMENT
& SYSTEM
SUPERVISOR
POWER
SECTION
3.3V
5.1V
12V LDO
5.1V LDO
3.39V REF
POWER GOOD
µP
MEMORY
PERIPHERALS
1/26



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L4992
ABSOLUTE MAXIMUM RATINGS
Symbol
VIN
VI
IIN
IOUT
TJ
Parameter
Power Supply Voltage on VIN
Maximum Pin Voltage to Pins 1, 24, 25, 32
Input Current Except V13IN and VIN
Output Current Digital Output
Junction Temperature
THERMAL DATA
Symbol
RTH J-amb
Parameter
Thermal Resistance Junction -Ambient
PIN CONNECTION (Top view)
Value
0 to 25
-0.5 to (VIN +5)
-1 to +1
-15 to +15
-55 to 150
Value
60
Unit
V
V
mA
mA
°C
Unit
°C/W
H5STRAP
VIN
REG5
V5SW
V5SNS
I5SNS
COMP5
SOFT5
32 31 30 29 28 27 26 25
1 24
2 23
3 22
4 21
5 20
6 19
7 18
8 17
9 10 11 12 13 14 15 16
H3STRAP
(*)
REG12
V13IN
V3SNS
I3SNS
COMP3
SOFT3
D96IN377
(*)TO BE CONNECTED TO PIN13
BLOCK DIAGRAM
SOFT5
SOFT3
8 17
I5SNS
V5SNS
COMP5
6
5
7
SLOPE
+
ERROR SUMMING
-
+
-
+
SOFT
SOFT
I5SNS V5SNS V3SNS I3SNS
ERROR SUMMING
+
-
+
-
+
SLOPE
19
I3SNS
20
V3SNS
18
COMP3
1
H5STRAP
-
VREF
OVER CURRENT
COMPARATOR
+
OVER CURRENT
COMPARATOR
+
-
VREF
24
H3STRAP
32
H5GATE
31
H5SRC
Hside
REG5
CONTROL
LOGIC
-
ZERO CROSSING
COMPARATOR
+
-
-
ZERO CROSSING
COMPARATOR
+
-
CONTROL
LOGIC
Hside
REG5
25
H3GATE
26
H3SRC
R5GATE
PGND5
30
29
Lside
PULSE SKIPPING
COMPARATOR
+
-
PULSE SKIPPING
COMPARATOR
+
-
Lside
27
R3GATE
28
PGND3
REG5
3
W5SW
VIN
4
2
VREF 12
SGND
13
LINEAR
REGULATOR
-
+
SWITCH
COMPARATOR
VREF BUFFER
+
-
V5SNS
OVERVOLT
COMPARATOR
UNDERVOLT
COMPARATOR
4.7V
POWER MANAGEMENT
&
SYSTEM SUPERVISOR
VREF
16 11 10
14 9
RUN3 RUN5 PWROK NOSKIP CRST
13V UV Comp
+
-
13V
21
V13IN
VREF
+
-
OSCILLATOR &
SYNCHRONIZATION
22
REG12
LDO
REG12
15
OSC
D96IN375
2/26



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L4992
PIN FUNCTIONS
N. Name
Description
1 H5STRAP +5.1V section bootstrap capacitor connection
2 VIN Device supply voltage. From 5.5 to 25V
3 REG5 +5V regulator supply. Used mainly for bootstrap capacitors. It should be bypassed to ground.
4 V5SW Alternative device supply voltage. When the +5.1V section is operating, the device is no
longer powered through VIN but through this pin.
5 V5SNS This pin connects to the (-) input of the +5.1V internal current sense comparator
6 I5SNS This pin connects to the (+) input of the +5.1V internal current sense comparator
7 COMP5 Feedback input for the +5.1V section.
8 SOFT5 Soft-start input of the +5.1V section. The soft-start time is programmed by an external
capacitor connected between this pin and SGND. Approximately, 1ms/nF @ full load.
9 CRST Input used for start-up and shut-down timing. A capacitor defines a time of 2ms/nF.
10 PWROK Power-good diagnostic signal. This output is driven high when both switching sections are
enabled and running properly, after a delay defined by the CRST capacitor.
11 RUN5 Control input to enable/disable the 5.1V section. A high level (>2.4V) enables this section, a
low level (<0.8V) shuts it down
12 VREF Internal +3.39V high accuracy voltage generator. It can source 5mA to external load. Bypass
to ground with a 4.7µF capacitor to reduce noise.
13 SGND Signal ground. Reference for internal logic circuitry. It must be routed separately from high
current returns.
14 NOSKIP Pulse skipping mode control. A high level (>2.4V) disables pulse skipping at low load current,
a low level (<0.8V) enables it.
15
OSC
Oscillator frequency control: connect to 2.5V to select 300KHz operation, to ground or to 5V
for 200KHz operation. A proper external signal can synchronize the oscillator
16 RUN3 Control input to enable/disable the +3.3V section. A high level (>2.4V) enables this section, a
low level (>0.8V) shuts it down.
17 SOFT3 Soft-start input for the 3.3V section. The soft-start time is programmed by an external
capacitor connected between this pin and GND. Approximately, 1ms/nF @full load.
18 COMP3 Feedback input for the +3.3V section
19 I3SNS This pin connects to the (+) input of the +3.3V internal current sense comparator
20 V3SNS This pin connects to the (-) input of the +3.3V internal current sense comparator
21 V13IN 12V regulator input supply voltage, included between 13 and 20V. This voltage can be
supplied by a flyback winding on +3.3V inductor
22 REG12 12V regulator output voltage. It can source up to 150mA to an external load
23 SGND To be connected to pin 13
24 H3STRAP +3.3V section bootstrap capacitor connection
25 H3GATE Gate- driver output for the +3.3V high-side N-MOS
26 H3SRC +3.3V high-side N-MOS source connection
27 R3GATE Gate- driver output for the +3.3V low- side N-MOS (synchronous rectifier).
28 PGND3 Current return for +3.3V section drivers
29 PGND5 Current return for +5.1V section drivers
30 R5GATE Gate-driver output for the +5.1V low-side N-MOS (synchronous rectifier).
31 H5SRC +5.1V high-side N-MOS source connection
32 H5GATE Gate-driver output for the +5.1V high-side N-MOS
3/26



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L4992
ELECTRICAL CHARACTERISTICS (VIN = 12V; TJ = 25°C; VOSC = GND; unless otherwise specified.)
Symbol
Parameter
Test Condition
DC CHARACTERISTICS
VIN Input Supply Voltage
I2 Operating Quiescent Current
I2 Stand-By Current
R5GATE = R3GATE = OPEN
H5GATE = H3GATE = OPEN
RUN3 = RUN5 = REG5
(DRIVERS OFF)
RUN3 = RUN5 = GND
VIN = 12V
VIN = 20V
+5.1V PWM CONTROLLER SECTION
V5OUT (*) V5SNS Feedback Voltage
V6 - V5
V6 - V5
V5
Over-Current Threshold Voltage
Pulse Skipping Mode
Thereshold Voltage
Over Voltage Threshold ON
V5SNS
Under Voltage Threshold ON
V5SNS
VIN = 5.5 to 20V;
VI5SNS - VV5SNS = 0 to 70mV
VSOFT5 = 4V
VIN > 6.8V
VIN < 5.8V
+3.3V PWM CONTROLLER SECTION
V3OUT (*) V3SNS Feedback Voltage
V19 - V20
V19 - V20
V20
Over Current Threshold Voltage
Pulse Skipping Mode Threshold
Voltage
Over Voltage Threshold ON
V3SNS
Under Voltage Threshold ON
V3SNS
VIN = 5.5 to 20V;
VI3SNS - VV3SNS = 0 to 70mV
VSOFT3 = 4V
VIN = 5.5 to 20V;
PWM CONTROLLERS CHARACTERISTICS (BOTH SECTIONS)
FOSC
Switching Frequency Accuracy OSC = REG5/2
OSC = 0 or REG5
V15 Voltage Range for 300kHz
Operation
TOFF
Dead Time
TOV Overvoltage Propagation Time V5SNS to PWROK or
V3SNS to PWROK
TUV Undervoltage Propagation Time V5SNS to PWROK or
V3SNS to PWROK
I8, I17
Soft Start Charge Current
V8, V17 Soft Start Clamp Voltage
(*) Guaranteed by design, not tested in production
Min. Typ. Max. Unit
5.5 25 V
1.35 mA
50 100 µA
60 120
4.85
80
14
7
5.35
4.54
5.13
100
26
13
5.55
4.69
5.25
120
38
19
5.77
4.87
V
mV
mV
mV
V
V
3.285 3.39 3.495
80 100 120
14 26 38
3.55 3.7 3.85
3.02 3.14 3.27
V
mV
mV
V
V
255 300 345 kHz
170 200 230 kHz
2.4 2.6 V
300 375 450
ns
1.25 µs
1.5 µs
3.2 4 4.8 µA
4V
4/26




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