MAX38913, MAX38914

4µVRMS Ultra-Low-Noise 1A LDO with Two-

Level Output Voltage Selection

www.analog.com

Analog Devices | 13

VEN2

VEN1

VOUT

3.3V

1.8V

VIN = 3.6V

1.8V

DISABLED

MODE 1

MODE 2

PASS-

THROUGH

MODE 2

DISABLED

[EN2:EN1] MODE SELECT

00: OFF

01: MODE1

11: MODE2

10: PASS-THROUGH

Figure 1. Modes of Operation (MAX38913)

VEN2

VEN1

VOUT

2.3V

2.0V

VIN = 3.3V

2.0V

DISABLED

MODE 1

MODE 2

PASS-

THROUGH

MODE 2

DISABLED

[EN2:EN1] MODE SELECT

00: OFF

01: MODE1

11: MODE2

10: PASS-THROUGH

Figure 2. Modes of Operation (MAX38914)

Pass-Through Mode

The MAX38913/MAX38914 includes a pass-through mode where the output pass device is turned on hard, shorting the

output to the input. In this mode, quiescent current is reduced to 115µA. The controller remains on to support a current-

limiting circuit.

The output voltage always slews in the pass-through mode and back to regulation mode at the same rate. The slew rate

is defined by the CBYP capacitor used in application, and can be calculated as:

������������������������������

������������

=

������������������������_������������������������

������������������������

=

50������������

������������������������

As the device transitions in and out of the pass-through mode, the regulator is enabled until slewing is completed. After

slewing is completed, the controller is disabled to save power while the current-limit detector remains on. The device limits

the current in the pass-through mode to about a 2A level.

If the current-limit circuit trips in the pass-through mode, the regulator enables and tries to regulate the output voltage

back into dropout with the feedback held low, delivering load current up to the level of the current limit in dropout—about

1.4A. During current limiting, it is common for the device to go into thermal shutdown, and also for the output to turn on

and off as the die temperature slews between +150°C and +165°C.