Applications Information

Input Power Supply and Capacitance

Connect both IN inputs together externally. IN powers

the internal control circuitry and charge pump for the

with a 1µF ceramic capacitor. When driving inductive

loads or operating from inductive sources, which may

occur when the device is powered by long leads or PC

traces, larger input bypass capacitance is required to

prevent voltage spikes from exceeding the absolute

maximum ratings during short-circuit events.

Output Capacitor

Bypass OUT to GND with a 4.7µF ceramic capacitor for

local decoupling. Additional bulk capacitance (up to

470µF) reduces output-voltage transients under dynam-

ic load conditions. Using output capacitors greater than

470µF might assert FAULT if the current limit cannot

charge the output capacitor within the 20ms fault-

blanking period. In addition to bulk capacitance, small-

value (0.1µF or greater) ceramic capacitors improve the

output’s resilience to electrostatic discharge (ESD).

Driving Inductive Loads

A wide variety of devices (mice, keyboards, cameras,

and printers) typically connect to the USB port with

cables, which might add an inductive component to the

load. This inductance causes the output voltage at the

USB port to oscillate during a load step. The

MAX1562/MAX1562H/MAX1563 drive inductive loads,

but avoid exceeding the device’s absolute maximum

ratings. The load inductance is usually relatively small,

and the MAX1562/MAX1562H/MAX1563s’ input

includes a substantial bulk capacitance from an

upstream regulator, as well as local bypass capacitors,

limiting overshoot. If severe ringing occurs because of

large-load inductance, clamp the MAX1562/MAX1562H/

MAX1563 outputs below +6V and above -0.3V.

Turn-On and Turn-Off Behavior

When turned on, the MAX1562/MAX1562H/MAX1563 out-

put ramps up over 2.5ms to eliminate load transients on

the upstream power source. When turned off, the output

ramps down for 800µs. Under fault conditions, the output

of the switches turns off rapidly to provide maximum safe-

ty for the upstream power source and downstream

devices. Internal blocks shut down to minimize supply

current when the switch is off.

Programmable 4A USB Current-Limited

Switches with Autoreset and Fault Blanking

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Table 2. Current Limiting and Fault Behavior

CONDITION

MAX1562/MAX1562H/MAX1563 BEHAVIOR

Output Short-Circuit

• If a short is detected at the output, the channel turns off, and the blanking timer begins. FAULT

remains high during the blanking timeout period.

is removed before the 20ms short-circuit blanking timeout period, the next ramped current pulse soft-

starts the output. FAULT remains high.

• If the short-circuit persists after the fault-blanking period. FAULT goes low, autoreset mode begins,

and the output sources 25mA.

• If the output voltage rises above 0.5V for 20ms, the channel resets, the output turns on, and FAULT

goes high.

Output Overload Current

high during the blanking timeout period.

fault occurs.

• If overcurrent persists after 20ms, FAULT goes low, autoreset mode is enabled, and the output

sources 25mA.

• If the output voltage rises above 0.5V for 20ms, the channel resets, the output turns on, and

FAULT goes high (see the Overload Response into 1.4

Ω graph in the Typical Operating

Characteristics section).

Thermal Fault

• A junction temperature of +160

does not apply for thermal faults) and turns off the switch. When the junction cools by 15°C, the

thermal fault is cleared and FAULT goes high. Note that if other fault conditions are present when

a thermal fault clears, those fault states take effect.