LT1431
10
1431fe
Typical applicaTions
5V Power Supply Monitor with ±500mV
Window and 50mV Hysteresis
Transfer Function
High Efficiency Buck Converter E = 85% to 89%
COLL
REF
GND-F
V
+
GND-S
10Ω**
“HIGH” FOR
OVER VOLTAGE OR
UNDER VOLTAGE
5k
1N4148
COLL
REF
GND-F
V
+
GND-S
10Ω**
5k
4k*1k6k*1k
*DETERMINES WINDOW SIZE
V = (R – 5k)(0.5mA)
**SETS HYSTERESIS
LT1431 TA13
LT1431 LT1431
V
IN
0
0
OUT
1
2
3
4
1
2 3 4
LT1431 TA14
5 6
5
COLL
12
65
REF
R
MID
3
Q3
2N3904
4
8
7
V
+
R
TOP
R8*
24.9k
COMP
GND-FGND-S
LT1431CN8
+
+
+
R2
1k
C3
0.1µF
C5
0.047µF
C4
0.033µF
R6*
23.7k
5V
2.5A
C6
470µF
16V
0.12Ω
ESR
R7*
24.9k
1431 TA15
Q2
2N3904
D2
BAT85
D4
BAT85
R1
470k
C2
4.7µF
35V
TANT
L1
50µH 3A
R5
680Ω
Q1
VN2222LL
RUN = 0
SHUTDOWN > 3V
R4
100Ω
R3
10k
NOTES: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTANCES ARE IN Ω, 0.25W, 5%
2. ALL CAPACITANCES ARE IN µF, 50V, 10%
3. SHUTDOWN LOGIC STATE MUST BE DEFINED BY A LOGIC GATE OR BY TYING TO GND
1
2
RTN
OFF
V
IN
D1
BAT85
C1
220µF
35V
D3
MBR330
BOLD LINES INDICATE HIGH CURRENT PATHS
*1% FILM RESISTORS
C1: NICHICON UPL1V221MPH
C3, C4, C5: WIMA MKS-2
C6: NICHICON UPL1C471MPH6
D1, D2: PHILIPS BAT85
D3: MOTOROLA MBR330
L1: COILTRONICS CTX50-3-MP
LT1170
V
IN
V
C
GND
V
SW
FB
3 1
2
4
5
