Datasheet

UC1903
+VIN
REFERENCE
CIRCUIT
1.25V
Q2
Q1
Q3
R1
R2
R3
15 W
2.5kW
2.5kW
2.5V
OUTPUT
R
A
R
S
V
ADJ
BIAS
CANCELLATION
ANDMIRROR
CIRCUITS
I =
O
V
ADJ
R4
R4
8kW
R5
R6
R7
R8
1.84kW
0.16kW
0.16kW
1.84kW
I
OC
I
OD
Q5
Q4
I
OB
I
OA
TO
OVHYSTERESIS
CONTROL
OVTHRESHOLD
FAULTWINDOW
THREAHOLDandHYSTERESIS
CIRCUITS
UVTHRESHOLD
TO
UVHYSTERESIS
CONTROL
Typical Characteristics
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-55 -35 -15 5 25 45 65 85 105 125
T -JunctionTemperature-°C
J
ReferenceChange-%
Typical2.5VReference
vs
TemperatureCharacteristic
40
Delay-ms/ Fm
-55 -35 -15 5 25 45 65 85 105 125
T -JunctionTemperature-°C
J
TypicalFaultDelay
vs
TemperatureCharacteristic(C 270pF)
DELAY
≥
35
30
25
20
UC1903
UC2903
UC3903
www.ti.com ........................................................................................................................................ SLUS233A – OCTOBER 1999 – REVISED SEPTEMBER 2008
Block Diagram
A. The UC1903 fault window circuitry generates OV and UV thresholds centered around the 2.5-V reference. Window
magnitude and threshold hysteresis are proportional to the window adjust input voltage at Pin 4.
Figure 1. Operation and Application Information
Copyright © 1999 – 2008, Texas Instruments Incorporated Submit Documentation Feedback 5
Product Folder Link(s): UC1903 UC2903 UC3903