LT1640HIS8#TR Linear Technology, LT1640HIS8#TR Datasheet - Page 12

• Manufacturer Part Number: LT1640HIS8#TR
• Description: IC CTRLR HOTSWAP NEG VOLT 8SOIC
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LT1640HIS8#TR

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: -10 V ~ -80 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS
LT1640L/LT1640H
The new threshold voltage when the input moves from low
to high is:
where V
The new threshold voltage when the input moves from
high to low is:
where V
The new hysteresis value will be:
With R1 = 562k, R2 = 16.9k and R3 = 1.62M, V
and V
(from low to high) and 37.6V (from high to low). The
hysteresis is 5.4V. A separate resistor divider should be
used to set the overvoltage threshold given by:
12
V
V
UV HL
HYS
V
UV LH
,
UVHY
,
UVH
UVL
V
UVHY
V
= 20mV, the undervoltage threshold will be 43V
UVL
V
UVH
is typically 1.223V.
is typically 1.243V.
R
R
R
2
2
2
•
•
U
R
R
•
R
3
3
3
* DIODES INC. SMAT70A
– 48V
GND
R
R
R R
R R
INFORMATION
R
2
2
U
1
1
R R
*
2
•
•
•
•
1
GND
R
R
•
•
R
3
3
3
3
R4
R5
R6
(SHORT PIN)
3
3
R R
R R
3
2
R R
1
1
W
•
•
1
UV
OV
LT1640H
•
3
+
–
2
2
V
4
2
1
EE
V
–
Figure 11. Active High Enable Module
PG
R1
GATE
V
V
SENSE
2
GATE
GATE
U
+
–
4
5
= 13.5V
•
•
R
R
R
R
V
C1
3
DD
1
1
3
6.5k
8
R7
GATE
Q1
V
EE
Q3
6
R2
With R4 = 506k, R5 = 8.87k and V
overvoltage threshold will be 71V.
PWRGD/PWRGD Output
The PWRGD/PWRGD output can be used to directly en-
able a power module when the input voltage to the module
is within tolerance. The LT1640L has a PWRGD output for
modules with an active low enable input, and the LT1640H
has a PWRGD output for modules with an active high
enable input.
When the DRAIN voltage of the LT1640H is high with
respect to V
turned off and R7 and Q2 clamp the PWRGD pin one diode
drop ( 0.7V) above the DRAIN pin. Transistor Q2 sinks
the module’s pull-up current and the module turns off.
When the DRAIN voltage drops below V
shorting the bottom of R7 to DRAIN and turning Q2 off.
The pull-up current in the module then flows through R7,
pulling the PWRGD pin high and enabling the module.
PWRGD
Q2
R3
DRAIN
V
OV
C2
1
7
2 1N4148
V
OVH
EE
+
R
(Figure 11), the internal transistor Q3 is
4
1640 F11
R
C3
5
R
ENABLE MODULE
5
V
V
ON/OFF
ACTIVE HIGH
IN
IN
+
–
V
V
OUT
OUT
+
–
OVH
PG
, Q3 will turn on,
= 1.223V, the
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