鈥?/div>
Thermal Shutdown
DESCRIPTION
The UCC3916 SCSI termpower manager provides complete power man-
agement, hot swap capability, and circuit breaker functions with minimal ex-
ternal components. For most applications, the only external component
required to operate the device, other than supply bypassing, is a timing ca-
pacitor which sets the fault time.
The current trip level is internally set at 1.65A, and the maximum current
level is also internally programmed for 2A. While the output current is below
the trip level of 1.65A, the internal power MOSFET is switched on at a nom-
inal 220m鈩? When the output current exceeds the trip level but remains
less than the maximum current level, the MOSFET remains switched on,
but the fault timer starts charging CT. Once the fault time is reached, the cir-
cuit will shut off for a time which equates to a 3% duty cycle. Finally, when
the output current reaches the maximum current level, the MOSFET transi-
tions from a switch to a constant current source.
The UCC3916 is designed for uni-directional current flow, emulating a diode
in series with the power MOSFET.
The UCC3916 can be put in a sleep mode, drawing only 1碌A of supply cur-
rent.
Other features include thermal shutdown and low thermal resistance Small
Outline Power package.
BLOCK DIAGRAM
1
REVERSE VOLTAGE
COMPARATOR
CHARGE
PUMP
MAXIMUM
CURRENT
LEVEL
2A
LINEAR
CURRENT
AMPLIFIER
CURRENT
TRIP LEVEL
1.65A
OVER CURRENT
COMPARATOR
50mV
+
OUTPUT
CURRENT SENSE
H=OPEN
POWER
FET
VIN
4V TO 6V
ON TIME CONTROL
3% DUTY CYCLE
THERMAL
SHUTDOWN
INTERNAL
BIAS
2
3
6
7
4
+
鈥?/div>
5
SHTDWN
UDG-99172
1.5V
8
OUTPUT
GND GND GND GND CT
4 HEATSINK PINS
SLUS206A - JANUARY 2000
1
2
3
