鈥?/div>
Power SOIC and TSSOP, Low
Thermal Resistance Packaging
DESCRIPTION
The UCC3915 Programmable Hot Swap Power Manager provides com-
plete power management, hot swap capability, and circuit breaker functions.
The only external component required to operate the device, other than
power supply bypassing, is the fault timing capacitor, C
T
. All control and
housekeeping functions are integrated, and externally programmable.
These include the fault current level, maximum output sourcing current,
maximum fault time, and startup delay. In the event of a constant fault, the
Internal fixed 2% 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
sourcing current to 1A above the trip level or to a full 4A of output current
for fast output capacitor charging.
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 CT.
Once CT charges to a preset threshold, the switch is turned OFF, and re-
mains OFF for 50 times the programmed fault time. When the output cur-
rent reaches the maximum sourcing level, the MOSFET transitions from a
switch to a constant current source.
BLOCK DIAGRAM
2
CHARGE
PUMP
MAX
CURRENT
LEVEL
LINEAR CURRENT
AMPLIFIER
OVER CURRENT
COMPARATOR
REVERSE VOLTAGE
COMPARATOR
30mV
+
3
CURRENT SENSE
H = OPEN
POWER
FET
*
VIN
IMAX 10
H = 4A
V
OUT
4A
1A
ABOVE
FAULT
CURRENT FAULT
LEVEL 0鈥? AMPS
ON TIME
CONTROL
2% DUTY
CYCLE
14
VOUT
15
0鈥?A
0.25
RES
THERMAL
SHUTDOWN
INTERNAL
BIAS
+
鈥?/div>
1.5V
1
SHTDWN
6
B3
7
B2
8
B1
9
B0
5
GND
4
13
12
11
CT
16
FAULT
* BODY DIODE
4 BIT DAC
HEAT SINK
GND PINS
Note: Pin numbers refer to DIL-16 and SOIC-16 packages.
UDG-99174
SLUS198A - FEBRUARY 2000
1
2
3
4
5
