Datasheet

MAX5948A/MAX5948B
Figure 11a shows how to program the undervoltage
and overvoltage trip thresholds using three resistors.
With R4 = 562kΩ, R5 = 9.09kΩ, and R6 = 10kΩ, the
undervoltage threshold is set to 37.2V (with a 37.8V
release from undervoltage) and the overvoltage is set
to 71.1V (with a 69.9V release from overvoltage).
More hysteresis can be added to the undervoltage
lockout with the circuit shown in Figure 11b. Resistor
R3 connected between GATE and UV lowers the sup-
ply undervoltage lockout threshold (supply voltage
decreasing) to:
where V
UVL
is typically 1.223V. The supply voltage to
release from undervoltage lockout (supply voltage
increasing) is:
where V
UVH
is typically 1.243V. The supply undervolt-
age lockout hysteresis is the difference, or:
where V
UVHY
is typically 20mV.
VV
R R RR RR
RR
V
R
R
UV HYS UVHY GATE,
=
×+×+×
×
⎛
⎝
⎜
⎞
⎠
⎟
+×
⎛
⎝
⎜
⎞
⎠
⎟
231312
23
1
3
∆
VV
RRRRRR
RR
UV LH UVH,
=
×+×+×
×
⎛
⎝
⎜
⎞
⎠
⎟
231312
23
VV
R R RR RR
RR
V
R
R
UV HL UVL GATE,
=
×+×+×
×
⎛
⎝
⎜
⎞
⎠
⎟
−×
⎛
⎝
⎜
⎞
⎠
⎟
231312
23
1
3
∆
-48V Hot-Swap Controllers
with External R
SENSE
12 ______________________________________________________________________________________
V
EE
V
DD
OV
UV
MAX5948A
MAX5948B
-48V RTN
-48V
V
UV
= 1.223
R4 + R5 + R6
R5 + R6
R4
R5
R6
-48V RTN
(SHORT PIN)
V
OV
= 1.223
R4 + R5 + R6
R6
Figure 11a. Undervoltage and Overvoltage Sensing
V
EE
SENSE
GATE
V
DD
UV
OV
MAX5948
-48V RTN
= 37.6VUV
-48V RTN
(SHORT PIN)
*
-48V
*DIODES INC. SMAT70A.
R1
562kΩ
1%
R4
506kΩ
1%
R2
16.9kΩ
1%
R5
8.87kΩ
1%
R7
0.02Ω
5%
R6
10Ω
5%
C1
150nF
25V
Q1
IRF530
R3
1.62MΩ
1%
= 43VUV
= 71VOV
Figure 11b. Programmable Hysteresis For Undervoltage