MAX1615EUK Datasheet, PDF (5/8 Pages) Maxim Integrated Products – High-Voltage, Low-Power Linear Regulators for Notebook Computers

High-Voltage, Low-Power Linear Regulators
for Notebook Computers
______________________________________________________________Pin Description
PIN
MAX1615
MAX1616
1
1
2
2
3
3
4
—
—
4
5
5
NAME
IN
GND
OUT
5/3
FB
SHDN
FUNCTION
Positive Input Voltage. Connect to a +4V to +28V supply.
Ground
Regulator Output
Preset Output Voltage Select. Connect to GND for 3.3V output or to OUT
for 5.0V output.
Feedback Input. Regulates to 1.24V nominally.
Shutdown, active low input. Connect to IN for automatic start up.
IN
VREF
OUT
SHDN
CURRENT
LIMIT
MAX1615
MAX1616
FB
5/3
GND
(MAX1616)
(MAX1615)
Figure 1. Functional Diagram
_______________Detailed Description
The MAX1615/MAX1616 low-quiescent-current linear
regulators are designed primarily for high input voltage
applications. The MAX1615 supplies a preselected 3.3V
or 5.0V output for loads up to 30mA. The MAX1616
provides an adjustable voltage from 1.24V to 28V. The
maximum output current is a function of the package’s
maximum power dissipation for a given temperature. A
5µA load is required to maintain output regulation.
The MAX1615’s output voltage is fed back through an
internal resistor voltage divider connected to OUT. Set
the output voltage to either 3.3V or 5.0V with the 5/3 pin.
Select the 5V output by connecting 5/3 to OUT, or the
3.3V output by connecting 5/3 to GND.
The MAX1616 uses external feedback, allowing the out-
put voltage to be set by external resistors (see Setting
the MAX1616 Output Voltage section). The typical FB
threshold is at 1.24V.
Shutdown
The device enters shutdown mode when SHDN is low.
In shutdown mode, the pass transistor, control circuit,
reference, and all biases turn off, reducing the supply
current to below 1µA. Connect SHDN to IN for automatic
start-up.
Current Limit
Output current is limited to 100mA (typical). The current
limit exceeds the 30mA (max) safe operating limit. The
output can be shorted to ground for 30 seconds without
damaging the part.
Thermal-Overload Protection
When the junction temperature exceeds T_J = +150°C,
the thermal sensor sends a signal to the shutdown
logic, turning off the pass transistor and allowing the IC
to cool. The thermal sensor turns the pass transistor on
again after the IC’s junction temperature cools by
+20°C (typical), resulting in a pulsating output during
continuous thermal-overload conditions.
Operating Region and Power Dissipation
Maximum power dissipation depends on the thermal
resistance of the case and circuit board, the tempera-
ture difference between the die junction and ambient
air, and the rate of air flow. The device’s power dissipa-
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