Positive High-Voltage, Hot-Swap Controllers with

Selectable Fault Management and Status Polarity

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9

Detailed Description

The MAX5934/MAX5934A are fully integrated hot-swap

controllers for positive supply rails. These devices allow

for the safe insertion and removal of circuit cards into

live backplanes without causing glitches on the back-

plane power-supply rail. During startup, the MAX5934/

MAX5934A act as current regulators using an external

sense resistor and MOSFET to limit the amount of cur-

rent drawn by the load.

The MAX5934A operates from a +9V to +80V supply

voltage range and has a default UVLO set to +8.3V.

The MAX5934 operates from a +33V to +80V supply

voltage range and has a default UVLO set to +31V. The

UVLO threshold is adjustable using a resistive divider

Figure 5).

The MAX5934/MAX5934A monitor input voltage, output

voltage, output current, and die temperature. These

devices feature three power-good outputs (PWRGD_)

to indicate status by monitoring the voltage at FB1,

FB2, and GATE (see the Power-Good (PWRGD_)

Detection section). PWRGD1 indicates an output-volt-

age status, PWRGD2 can be used to indicate an over-

voltage condition on the main power-supply rail, and

PWRGD3 asserts when GATE voltage has charged to

4.3V above the supply rail. PWRGD3 deasserts when

the TIMER voltage exceeds a 1.233V threshold in

response to an extended fault condition.

The MAX5934/MAX5934A control gate voltage on the

external MOSFET to limit load current at startup and at

overload to a value determined as:

MAX5934

MAX5934A

ON

OUT

GATE

SENSE

16

14

11

9

4

6

5

7

12

8

M1

R1

1k

Ω, 5%

0.025

Ω

C1

10nF

10

Ω

5%

R4

59k

Ω

1%

R6

24k

Ω

5%

R7

24k

Ω

5%

R10

1k

Ω

1%

R9

90k

Ω

1%

R2

49.9k

Ω

1%

R3

3.4k

Ω

1%

0.68

µF

R5

3.57k

Ω

1%

FB1

2

10

1

3

15

PWRGD1

PWRGD2

TIMER

LATCH/RETRY

FB2

PWRGD3

PWRGD1

PWRGD2

PWRGD3

DC

GND

POL_SEL

IRF530

Figure 5. Application Circuit