-100V, SOT23/TDFN, Simple Swapper

Hot-Swap Controllers

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5

Detailed Description

The MAX5900/MAX5901 are integrated hot-swap con-

troller ICs contained in 6-pin SOT23/TDFN packages.

They allow a board to be safely hot plugged into a live

backplane without causing a glitch on the power-sup-

ply rail. They are well suited for -48V telecom power

systems, allowing a cost-effective, simple, and com-

pact design. The MAX5900/MAX5901 operate from -9V

to -100V to cover the standard telecom voltage range,

and to serve more generalized applications. These

devices require only an external n-channel power MOS-

FET to provide hot-swap control. Figure 1 shows a

functional diagram of the MAX5900/MAX5901.

The MAX5900/MAX5901 control an external n-channel

power MOSFET placed in the negative power-supply

pathway. When power is first applied, the MAX5900/

MAX5901 keep the MOSFET turned off. The MAX5900/

MAX5901 hold the MOSFET off indefinitely if ON/OFF is

held low, if the supply voltage is below the undervolt-

age lockout level, or if the die temperature exceeds

+125°C. If none of these conditions exist for 300ms

(typ), the MAX5900/MAX5901 begin to gradually turn

on the MOSFET. During this turn-on phase, the

MAX5900/MAX5901 slowly enhance the MOSFET,

Figure 1. Functional Diagram

ON/OFF

GND

MAX5900

MAX5901

GATE

34.5k

Ω*

466k

Ω*

1k

Ω*

828k

Ω*

DRAIN

*RELATIVE TOLERANCE

±1%, ABSOLUTE TOLERANCE ±20% TYPICAL.

CONTROL

LOGIC

PGOOD

(PGOOD)

( ) ARE FOR THE MAX5901 ONLY.

3V

N

PIN

MAX5900

MAX5901

NAME

FUNCTION

11

Negative Supply Voltage Input and External n-Channel MOSFET Source

Connection

2

2

DRAIN

Drain Sense Input for External n-Channel MOSFET. Connect DRAIN as close as

possible to the MOSFET’s drain and use wide circuit traces to assure good

thermal coupling between the MAX5900/MAX5901 and the MOSFET (see the

Layout Guidelines section).

3

3

GATE

Gate Drive Output for External n-Channel MOSFET

4

4

GND

Ground Connection.

5—

PGOOD

Power-Good Output. PGOOD is an n-channel, open-drain, active-low output,

—

5

PGOOD

Power-Good Output. PGOOD is an n-channel, open-drain, active-high output,

6

6

ON/OFF

or leave unconnected to enable the device. Drive ON/OFF below 1V to disable

the device. ON/OFF is also used to adjust the UVLO threshold. See the Under-

voltage Lockout section in the Applications Information. Internally clamped to

nominally 3V through a 1k

Ω resistor (see Figure 1).

—

—

EP

Pin Description