MAX1562_09 Datasheet, PDF (10/14 Pages) Maxim Integrated Products – Programmable 4A USB Current-Limited Switches with Autoreset and Fault Blanking

Programmable 4A USB Current-Limited
Switches with Autoreset and Fault Blanking
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.
Layout and Thermal Dissipation
Keep all traces as short as possible to reduce the effect
of undesirable parasitic inductance and optimize the
switch response time to output short-circuit conditions.
Place the input and output capacitors no more than
5mm from the device leads. Connect IN and OUT to the
power bus with short traces. Wide power bus planes at
IN and OUT provide superior heat dissipation.
Calculate the power dissipation for a normal loaded
condition as follows:
P = (I_OUT)² x R_ON
At a 3A operating current and the maximum on-resis-
tance of the switch (50mΩ), the power dissipation is:
P = (3A)² x 0.05Ω = 450mW
The worst-case power dissipation occurs when the out-
put current is just below the current-limit threshold (set
to 3A in this example) with an output voltage greater
than +1V. In this case, the power dissipated in the
switch is the voltage drop across the switch multiplied
by the current limit:
P = I_LIM x (V_IN - V_OUT)
For a +5V input and +1V output, the maximum power
dissipation is:
P = 3A x (5V - 1V) = 12W
Because the package power dissipation is 471mW for
the MAX1562/MAX1562H and 1.35W for the MAX1563,
MAX1563 Functional Diagram
ON
CHARGE
SEL
PUMP
IN
IN
FAULT
MAX1563
THERMAL
SHUTDOWN
ILIM
OUT
25mA
FAULT LOGIC
20ms TIMERS
ULVO
OSC
25kHz
BIAS
REF
GND
the devices’ die temperature exceeds the +160°C ther-
mal-shutdown threshold, and the switch output shuts
down until the junction temperature cools by 15°C. The
duty cycle and period are strong functions of the ambi-
ent temperature and the PC board layout.
If the output current exceeds the current-limit threshold,
or the output voltage is pulled below the short-circuit
detect threshold, the MAX1562/MAX1562H/MAX1563
enter a fault state for 20ms, after which autoreset mode
is enabled and 25mA is sourced by the output. For a
+5V input, OUT short-circuited to GND, and autoreset
mode active, the power dissipation is as follows:
P = 0.025A x 5V = 0.125W
Typical Application Circuit
INPUT
+4V TO +5.5V
1μF
OFF
ON
IN
FAULT
IN
MAX1563
ON
SEL
OUT
ISET
OUT
GND
100kΩ
USB
PORT
4.7μF*
*USB APPLICATIONS MAY REQUIRE
ADDITIONAL BULK CAPACITANCE.
Pin Configurations
TOP VIEW
+
ON (ON) 1
FAULT 2
GND 3
MAX1562
MAX1562H
ISET 4
SO
() FOR MAX1562H.
8 OUT
7 IN
6 OUT
5 IN
OUT 1
N.C. 2
SEL 3
IN
N.C. OUT
12
11
10
+
MAX1563
4
5
6
ON FAULT GND
THIN QFN
4 mm x 4 mm
9 IN
8 N.C.
7 ISET
Chip Information
TRANSISTOR COUNT: 1833
PROCESS: BiCMOS
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