Rainbow Electronics MAX1563 - Manual (Page 7)

Detailed Description
The MAX1562/MAX1562H/MAX1563 family comprises a
programmable current-limited switch designed for USB
and hot-swap applications. The MAX1563 can be pro-
grammed for loads up to 4A, and the MAX1562/
MAX1562H can be programmed for loads up to 3A. The
current limit is programmed using a single resistor. A fault
output notifies the host when the current-limit, short-cir-
cuit, UVLO, or thermal-shutdown threshold is exceeded.
A built-in current limit protects the load and the source
in the event of an overload condition. In addition, a
built-in short-circuit detection circuit pulses the output if
the output is less than 1V (typ), resulting in a lower RMS
output current and reduced power dissipation in the
device. Thermal shutdown protects the device in the
event of a prolonged overload or short-circuit condition.
An internal micropower charge pump generates the
high-side supply needed for driving the gate of the
internal low-R
ON NMOS switch.
Fault blanking allows the MAX1562/MAX1562H/
MAX1563 family to handle USB loads that may not be
fully compliant with USB specifications. USB loads with
additional bypass capacitance or large startup currents
can be successfully powered while protecting the
upstream power source. If the switch brings up the
load within the blanking period (20ms typ), FAULT is
not asserted. In the event of a current-limit event, cur-
rent through the switch is regulated at the current-limit
target. Below approximately 1V, the short-circuit current
limit is 30% higher than the programmed current limit.
Current-Limit Programming
The MAX1562/MAX1562H/MAX1563 continuous current
limit is set by selecting the value of R
ISET
based on the
following equation:
I
LIM
= 17120 / R
ISET
Choose R ISET with resistor values between 4.22k
Ω to
16k Ω. Resistor values greater than 16kΩ significantly
degrade current-limit accuracy. For the MAX1562/
MAX1562H, the minimum R
ISET value is 5.76k
Ω. This
corresponds to a 3A current limit, which is limited by
the 8-pin SO’s maximum power dissipation.
MAX1562/MAX1562H/MAX1563
Programmable 4A USB Current-Limited
Switches with Autoreset and Fault Blanking
_______________________________________________________________________________________ 7
Pin Description
PIN
MAX1562
MAX1562H
MAX1563
NAME FUNCTION
1 4 ON ( ON)
Switch On/Off Control Input. The active polarity of ON is low for the MAX1562 and high
for the MAX1562H. For the MAX1563, the active polarity of ON is set by SEL.
2 5 FAULT
Fault Indicator Output. FAULT is an open-drain output that asserts low when the switch
enters a sustained (>20ms) current limit. FAULT goes low immediately during thermal
shutdown or an undervoltage input. Note that during severe short conditions,
FAULT
goes low immediately since there is typically also a brief undervoltage transient.
3 6 GND Ground
4 7 ISET
Current-Limit Input. Connect an external resistor from ISET to GND to set current limit,
where I
LIM = 17120 / R ISET .
5, 7 9, 12 IN
Power Input for Switch. Connect both IN inputs together and bypass with a 1µF
ceramic capacitor to GND. Load conditions might require additional bulk capacitance
to prevent fluctuation on the input source.
6, 8 1, 10 OUT
Power Output for Switch. Bypass OUT to GND with a 4.7µF ceramic capacitor. Load
conditions might require additional bulk capacitance. When disabled, OUT goes into
a high-impedance state.
— 2, 8, 11 N.C.
No Connection. Internally unconnected. Leave unconnected or use with other traces
to simplify PC board layout.
— 3 SEL
Polarity Control Input for ON. Drive SEL high for active-high enable. Drive SEL low for
active-low enable.