M
-100V SOT23 Simple Swapper Hot-Swap
Controllers
_______________________________________________________________________________________
5
Detailed Description
The MAX5900/MAX5901 are integrated hot-swap con-
troller ICs contained in 6-pin SOT23 packages. They
allow a board to be safely hot-plugged into a live back-
plane without causing a glitch on the power-supply rail.
They are well suited for -48V telecom power systems
allowing cost-effective, simple, and compact 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 MOSFET 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
undervoltage 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,
allowing the voltage on the load, i.e. the drain of the
V
EE
V
EE
ON/OFF
GND
MAX5900
MAX5901
828k
*
34.5k
*
GATE
DRAIN
CONTROL
LOGIC
PGOOD
(PGOOD)
( ) ARE FOR THE MAX5901 ONLY
* RELATIVE TOLERANCE
±
1%, ABSOLUTE TOLERANCE
±
20% TYPICAL
V
EE
3V
1k
*
N
466k
*
Figure 1. Functional Diagram
Pin Description
PIN
MAX5900
MAX5901
NAME
FUNCTION
1
1
V
EE
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
Layout
Guidelines
.
3
4
3
4
GATE
GND
Gate Drive Output for External N-Channel MOSFET
Ground Connection
5
—
PGOOD
Power-Good Output.
PGOOD
is an N-channel, open-drain, active-high output,
referenced to V
EE
.
—
5
PGOOD
Power-Good Output. PGOOD is an N-channel, open-drain, active-low output,
referenced to V
EE
.
6
6
ON/
OFF
ON
OFF
C ontr ol Inp ut. ON
OFF
i s r efer enced to V
E E
. D ve O N
OFF
ab ove 1.38V or
l eave unconnected to enab e the d evi ce. D ve ON
OFF
b el ow 1V to d sab e the
d evi ce. O N
OFF
i s al so used to ad ust the und er vol ag e l ockout ( U V LO) thr eshol d S ee
U nd er vol ag e Lockout
i n the
Ap p cati ons
secti on of thi s d ata sheet. Inter nal y cl am p ed
to nom nal y 3V thr oug h a 1k
r esi stor ( see Fi g ur e 1)