_______________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

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-

High-Voltage, Low-Power Linear Regulators

for Notebook Computers

_______________________________________________________________________________________

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______________________________________________________________Pin Description

1

IN

Positive Input Voltage. Connect to a +4V to +28V supply.

2

GND

Ground

4

5/3

Preset Output Voltage Select. Connect to GND for 3.3V output or to OUT

for 5.0V output.

5

SHDN

Shutdown, active low input. Connect to IN for automatic start up.

CURRENT

LIMIT

VREF

OUT

GND

SHDN

5/3

(MAX1615)

FB

(MAX1616)

IN

MAX1615

MAX1616

Figure 1. Functional Diagram

1

2

PIN

—

5

NAME

FUNCTION

MAX1615

MAX1616

3

OUT

Regulator Output

3

—

FB

Feedback Input. Regulates to 1.24V nominally.

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