SMH4802 Datasheet, PDF (11/20 Pages) Summit Microelectronics, Inc. – Programmable -48V Hot-Swap Controller with Forced Shut Down

APPLICATIONS INFORMATION (Continued)
SMH4802
Preliminary Information
SMX3200
Connector
Header
12
34
5 J1 6
78
9 10
FS
ISO2
R9 _Optional
100Ω _Forced
Shutdown
Components
R5 47kΩ
–48V Ret
R3
270kΩ
R2
10kΩ
R1
10kΩ
RD
R4
10kΩ
14
4 5 10 11
8 _UV
9 _OV
SMH4802
3
EN/TS
12
PG#
C5
0.01µF
R10
100kΩ
Q2
L14N1/TO
–48V Ret
5VREF
EN/TS
ENABLE#
7
6
2
1
–48V
R6
0.02Ω
C1
1µF
R7
10Ω
R8
10kΩ
C3
47nF
R11
100kΩ
C2
0.1µF
D1
Optional
DRAIN
SENSE
Components
–48V Switched
2062 Fig09
Figure 9. Example Applications Schematic.
Pin numbers reflect SOIC package.
Notes:
1. The 10Ω resistor (R7) must be located as close as possible to the MOSFET.
2. Optional interface circuit (Q2). The PG# output can be directly connected to the power module if the input voltage to the module is within
tolerance and the voltage on the PG# output doesn’t exceed 15V.
3. If the DRAIN SENSE signal is not used tie the pin directly to V (pin 7).
SS
The trip voltage of the UV and OV inputs is 2.5V relative
to VSS. Large value resistors can be used in the resistive
divider as the input impedance of UV and OV is very high.
The divider resistors should be high stability 1% metal-
film resistors to keep the under-voltage and over-voltage
trip points accurate.
Telecom Design Example
A hot-swap telecom application may use a 48V power
supply with a –25% to +50% tolerance (i.e., the 48V
supply can vary from 36V to 72V). The formulas for
calculating R1, R2, and R3 are as follows.
First, a peak current, IDMAX, must be specified for the
resistive network. The value of the current is arbitrary,
but it cannot be too high (self-heating in R3 becomes a
problem) or too low (the value of R3 becomes very large,
and leakage currents can reduce the accuracy of the OV
and UV trip points). The value of IDMAX should be ≥200µA
for the best accuracy at the OV and UV trip points. A value
SUMMIT MICROELECTRONICS, Inc.
2062 2.3 6/19/03
11