max5939eesat Maxim Integrated Products, Inc., max5939eesat Datasheet - Page 14

• Manufacturer Part Number: max5939eesat
• Description: -48v Hot-swap Controllers With External Rsense And High Gate Pulldown Current
• Manufacturer: Maxim Integrated Products, Inc.

• Determine load capacitance:
• Determine load current, I
• Select circuit-breaker current, for example:
• Calculate R
• Set allowable inrush current:
• Determine value of C2:
• Calculate value of C1:
• Determine value of R3:
-48V Hot-Swap Controllers with External
R
Figure 13. Using PWRGD to Drive an Optoisolator
14
Realize that I
erance.
SENSE
______________________________________________________________________________________
C
L
C
1
= C2 + C3 + module input capacitance
I
INRUSH
=
I
INRUSH
Component Selection Procedure:
(
SENSE
C
CB
2
+
varies ±20% due to trip-voltage tol-
≤
C
and High Gate Pulldown Current
R
I
:
*DIODES INC. SMAT70A
+
C
CB
GND
-48V
2
0 8
SENSE
gd
.
I
LOAD
=
= 2 x I
x
)
*
R
45
x
(SHORT PIN)
40
LOAD
SENSE
I
-48V RTN
=
INRUSH
6.49kΩ
µ
549kΩ



10kΩ
≤
mV
50
A x C
V
1%
1%
1%
LOAD
R4
R5
R6
I
CB
0 8
IN MAX
mV
.
.
(
−
x I
L
V
I
UV
OV
LOAD
GS TH
)
CB MIN
−
(
(
V
EE
V
)
GS TH
or
0.02Ω
5%
)
R1
(
SENSE
)



MAX5921A
MAX5921E
MAX5939A
MAX5939E
10Ω
5%
R2
V
DD
IRF530
GATE
Q1
1kΩ
5%
R3
• Set R2 = 10Ω.
• If an optocoupler is utilized as in Figure 14, deter-
Although the suggested optocoupler is not specified for
operation below 5mA, its performance is adequate for
36V temporary low-line voltage where LED current
would then be ≈2.2mA to 3.7mA. If R7 is set as high as
51kΩ, optocoupler operation should be verified over
the expected temperature and input voltage range to
ensure suitable operation when LED current ≈0.9mA for
48V input and ≈0.7mA for 36V input.
If input transients are expected to momentarily raise the
input voltage to >100V, select an input transient-voltage-
suppression diode (TVS) to limit maximum voltage on the
MAX5921/MAX5939 to less than 100V. A suitable device
is the Diodes Inc. SMAT70A telecom-specific TVS.
Select Q1 to meet supply voltage, load current, efficien-
cy, and Q1 package power-dissipation requirements:
mine the LED series resistor:
15nF
100V
C2
DRAIN
PWRGD
R
DPAK, D
7
=
R7
51kΩ
5%
I
D(ON)
V
BV
R
IN NOMINAL
3
2
3
PAK, or TO-220AB
DSS
(
100µF
≤
PWRGD
100V
≥ 3 x I
=
C3
I
LED
≥ 100V
150
C
2
LOAD
µ
≤
s
)
5
−
mA
2
V