Datasheet

MAX5920
Figure 11 shows how to program the undervoltage and
overvoltage trip thresholds using three resistors. With R4
= 549kΩ, R5 = 6.49kΩ, and R6 = 10kΩ, the undervoltage
threshold is set to 38.5V (with a 43V release from under-
voltage), and the overvoltage is set to 71V. The resistor-
divider also increases the hysteresis and overvoltage
lockout to 4.5V and 2.8V at the input supply, respectively.
PWRGD /PWRGD Output
The PWRGD (PWRGD) output can be used directly to
enable a power module after hot insertion. The
MAX5920A (PWRGD) can be used to enable modules
with an active-low enable input (Figure 13), while the
MAX5920B (PWRGD) is used to enable modules with
an active-high enable input (Figure 12).
The PWRGD signal is referenced to the DRAIN termi-
nal, which is the negative supply of the power module.
The PWRGD signal is referenced to V
EE
.
When the DRAIN voltage of the MAX5920A is high with
respect to V
EE
or the GATE voltage is low, the internal
pulldown MOSFET Q2 is off and the PWRGD pin is in a
high-impedance state (Figure 13). The PWRGD pin is
-48V Hot-Swap Controller
with External R
SENSE
12 ______________________________________________________________________________________
GATE
2V/div
NODE1
50V/div
1s/div
V
EE
SENSE
GATE DRAIN
V
DD
OV
UV
PWRGD
MAX5920A
-48V RTN
-48V RTN
(SHORT PIN)
*
-48V
*DIODES INC. SMAT70A.
R4
549kΩ
1%
R8
510kΩ
5%
R5
6.49kΩ
1%
R6
549kΩ
1%
R7
1MΩ
5%
R6
10kΩ
1%
R1
0.02Ω
5%
R3
1kΩ
5%
R2
10Ω
5%
C1
470nF
25V
C4
1µF
100V
N
Q1
IRF530
D1
1N4148
Q2
2N2222
Q3
ZVN3310
C2
3.3nF
100V
C3
100µF
100V
P
NODE1
Figure 10. Automatic Restart After Current Fault
V
EE
V
DD
OV
UV
MAX5920A
MAX5920B
-48V RTN
-48V
V
UV
= 1.255
R4 + R5 + R6
R5 + R6
R4
R5
R6
-48V RTN
(SHORT PIN)
3
2
4
8
V
OV
= 1.255
R4 + R5 + R6
R6
Figure 11. Undervoltage and Overvoltage Sensing