MAX1838EEE+ Maxim Integrated Products, MAX1838EEE+ Datasheet - Page 11

• Manufacturer Part Number: MAX1838EEE+
• Description: IC SW USB DUAL W/FB 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1838EEE+

• Applications: USB, Peripherals
• Voltage - Supply: 4 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -

during a load step. The MAX1838 is capable of driving
inductive loads, but avoid exceeding the device’s
absolute maximum ratings. Usually the load inductance
is relatively small, and the MAX1838’s input includes a
substantial bulk capacitance from an upstream regulator
as well as local bypass capacitors, limiting overshoot. If
severe ringing occurs due to large load inductance,
clamp the MAX1838’s output below 6V and above -0.3V.
In absence of faults, the MAX1838’s internal switches
turn on and off slowly under the control of the ON input.
The slow charge-pump switch-drive minimizes load tran-
sients on the upstream power source. Under thermal
fault and undervoltage lockout, the power device turns
off rapidly to protect the switch and the power source.
To optimize the switch response to output short-circuit
conditions, keep all traces as short as possible to reduce
the effect of undesirable parasitic inductance. Place
input and output capacitors no more than 5mm from
device leads. IN, AUX, and OUT pins must be connect-
ed with short traces to the power bus. Wide power bus
planes provide superior switch heat dissipation. While
the switches are on, power dissipation is small and the
package temperature rise is minimal. Calculate the
power dissipation for this condition as follows:
Figure 2. Typical Application Circuit
AUX
IN
0.1µF
0.1µF
Layout and Thermal Dissipation
Turn-On and Turn-Off Behavior
AUXA
AUXB
INA
INB
SEL
ON
GND
______________________________________________________________________________________
P = (I
MAX1838
OUT
Dual USB Switch with Fault Blanking
)
2
R
FAULTB
FAULTA
OUTB2
OUTB1
100kΩ
OUTA2
OUTA1
ON
ADJB
ADJA
67kΩ
10µF
10µF
100kΩ
67kΩ
OUTB
OUTA
For the normal operating current (I
imum on-resistance of the switch is 170mΩ, and the
power dissipation is:
The worst-case power dissipation occurs when the
switch is in current limit and the output is greater than
1V. In this case, the power dissipated in each switch is
the voltage drop across the switch multiplied by the cur-
rent limit:
For a 5V input and 1V output, the maximum power dissi-
pation per switch is:
Since the package power dissipation is only 667mW, the
MAX1838 die temperature will exceed the thermal shut-
down threshold and the switch output shuts down until
the junction temperature cools by 10°C. The duty cycle
and period are strong functions of the ambient tempera-
ture and the PC board layout.
A short circuit at the output causes the power dissipated
across the switch and the junction temperature to
increase. If the fault condition persists, the thermal-over-
load-protection circuitry activates, and the output shuts
down until the junction temperature decreases by 10°C
(see Thermal Shutdown ).
P = (0.5A)
P = (1.2A) (5.5V - 1V) = 5.4W
P = (I
2
x 0.170Ω = 43mW per switch
and Autoreset
LIM
) (V
IN
- V
OUT
OUT
)
= 0.5A), the max-
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