MAX5920 Maxim, MAX5920 Datasheet - Page 11

• Manufacturer Part Number: MAX5920
• Description: -48V Hot-Swap Controller with External RSENSE
• Manufacturer: Maxim

Figure 7b. Short-Circuit Protection Waveform
Figure 9. Circuit for Input Steps with Small C1
For C2 values less than 10nF, a positive voltage step on
the input supply can result in Q1 turning off momentarily,
which can shut down the output. By adding an additional
resistor and diode, Q1 remains on during the voltage
step. This is shown as D1 and R7 in Figure 9. The pur-
pose of D1 is to shunt current around R7 when the power
pins first make contact and allow C1 to hold the GATE
low. The value of R7 should be sized to generate an
R7 x C1 time constant of 33µs.
The UV and OV pins can be used to detect undervoltage
and overvoltage conditions. The UV and OV pins are
Undervoltage and Overvoltage
______________________________________________________________________________________
1ms/div
-48V RTN
-48V
*DIODES INC. SMAT70A.
*
(SHORT PIN)
-48V RTN
6.49kΩ
549kΩ
10kΩ
1%
1%
1%
R4
R5
R6
DRAIN
50V/div
GATE - V
10V/div
I
5A/div
D
(Q1)
UV
OV
Protection
V
EE
EE
0.02Ω
5%
R1
SENSE
-48V Hot-Swap Controller
R7
220Ω
5%
C1
150nF
25V
MAX5920A
V
DD
internally connected to analog comparators with 130mV
(UV) and 50mV (OV) of hysteresis. When the UV voltage
falls below its threshold or the OV voltage rises above its
threshold, the GATE pin is immediately pulled low. The
GATE pin is held low until UV goes high and OV is low,
indicating that the input supply voltage is within specifica-
tion. The MAX5920_ includes an internal lockout (UVLO)
that keeps the external MOSFET off until the input supply
voltage exceeds 15.4V, regardless of the UV input.
The UV pin is also used to reset the circuit breaker after
a fault condition has occurred. The UV pin can be pulled
below V
Figure 8. Voltage Step-On Input Supply
D1
BAT85
with External R
IRF530
GATE
Q1
R2
10Ω
5%
UVL
1kΩ
5%
R3
to reset the circuit breaker.
3.3nF
100V
C2
PWRGD
DRAIN
400µs/div
C3
0.1µF
100V
C4
22µF
100V
V
20V/div
DRAIN
20V/div
I
5A/div
D
SENSE
EE
(Q1)
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