application
INFO
available
UCC3912
Programmable Hot Swap Power Manager
FEATURES
•
Integrated 0.15Ω Power MOSFET
•
3V to 8V Operation
•
Digital Programmable Current Limit
from 0 to 3A
•
Electronic Circuit Breaker Function
•
1µA I
CC
when Disabled
•
Programmable on Time
•
Programmable Start Delay
•
Fixed 3% Duty Cycle
•
Uni-Directional Switch
•
Thermal Shutdown
•
Fault Output Indicator
•
Maximum Output Current can be set
to 1A above the Programmed Fault
Level or to a full 4A
•
Power SOIC, Low Thermal
Resistance Packaging
DESCRIPTION
The UCC3912 Hot Swap Power Manager provides complete power man-
agement, hot swap capability, and circuit breaker functions. The only com-
ponent required to operate the device, other than supply bypassing, is the
fault timing capacitor, C
T
. All control and housekeeping functions are inte-
grated, and externally programmable. These include the fault current level,
maximum output sourcing current, maximum fault time,and start-up delay.
In the event of a constant fault, the Internal fixed 3% duty cycle ratio limits
average output power.
The internal 4 bit DAC allows programming of the fault level current from 0
to 3A with 0.25A resolution. The IMAX control pin sets the maximum sour-
cing current to 1A above the fault level when driven low, and to a full 4A
when driven high for applications which require fast output capacitor charg-
ing.
When the output current is below the fault level, the output MOSFET is
switched on with a nominal on resistance of 0.15 . When the output cur-
rent exceeds the fault level, but is less than the maximum sourcing level,
the output remains switched on, but the fault timer starts charging C
T
.
Once C
T
charges to a preset threshold, the switch is turned off, and re-
mains off for 30 times the programmed fault time. When the output current
reaches the maximum sourcing level, the MOSFET transitions from a
switch to a constant current source.
(continued)
BLOCK DIAGRAM
2
CHARGE
PUMP
MAX
CURRENT
LEVEL
LINEAR CURRENT
AMPLIFIER
REVERSE VOLTAGE
COMPARATOR
30mV
+
3
CURRENT SENSE
H = OPEN
POWER
FET
VIN
IMAX 10
H = 4A
V
OUT
4A
1A
ABOVE
FAULT
14
OVER CURRENT
COMPARATOR
CURRENT FAULT
LEVEL 0–3 AMPS
ON TIME
CONTROL
3% DUTY
CYCLE
THERMAL
SHUTDOWN
INTERNAL
BIAS
+
–
1
SHTDWN
1.5V
VOUT
15
0–3A
0.25
RES
6
B3
7
B2
8
B1
9
B0
5
GND
4
13
12
11
CT
16
FAULT
UDG-99146
4 BIT DAC
HEAT SINK
GND PINS
SLUS241A - NOVEMBER 1999
TI [ TEXAS INSTRUMENTS ]
