LT1640AH LINER [Linear Technology], LT1640AH Datasheet - Page 11

• Manufacturer Part Number: LT1640AH
• Description: Negative Voltage Hot Swap Controller
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
Undervoltage and Overvoltage Detection
The UV (Pin 3) and OV (Pin 2) pins can be used to detect
undervoltage and overvoltage conditions at the power
supply input. The UV and OV pins are internally connected
to analog comparators with 20mV of hysteresis. When the
UV pin falls below its threshold or the OV pin rises above
its threshold, the GATE pin is immediately pulled low. The
GATE pin will be held low until UV is high and OV is low.
The undervoltage and overvoltage trip voltages can be
programmed using a three resistor divider as shown in
U
U
UV
UV
OV
Figure 10b. Programmable Hysteresis for Undervoltage Detection
* DIODES INC. SMAT70A
– 48V
GND
= 37.6V
= 43V
= 71V
W
Figure 10a. Undervoltage and Overvoltage Sensing
*
V
V
UV
OV
8.87k
506k
= 1.223
= 1.223
1%
1%
R4
R5
GND
U
16.9k
562k
R4 + R5+ R6
R4 + R5+ R6
1%
1%
R1
R2
(SHORT PIN)
R5 + R6
– 48V
R6
GND
1.62M
GND
1%
R3
R4
R5
R6
(SHORT PIN)
2
3
OV
UV
V
3
V
Figure 10a. With R4 = 562k, R5 = 9.09k and R6 = 10k, the
undervoltage threshold is set to 37V and the overvoltage
threshold is set to 71V. The resistor divider will also
amplify the 20mV hysteresis at the UV pin and OV pin to
0.6V and 1.2V at the input, respectively.
More hysteresis can be added to the UV threshold by
connecting resistor R3 between the UV pin and the GATE
pin as shown in Figure 10b.
DD
EE
8
4
3
2
1
0.02
5%
UV
OV
R1
LT1640AL /LT1640AH
LT1640AH
LT1640AL
SENSE
2
V
V
DD
EE
4
5
4
8
1640A F10a
C1
150nF
25V
IRF530
LT1640AL/LT1640AH
GATE
Q1
6
R6
10
5%
1640A F10b
11