Data Sheet

ADM7160

Rev. 0 | Page 13 of 24

THEORY OF OPERATION

The ADM7160 is an ultralow noise, low quiescent current, low

dropout linear regulator that operates from 2.2 V to 5.5 V and

can provide up to 200 mA of output current. The ADM7160

consumes a low 265 μA of quiescent current (typical) at full load.

Shutdown current consumption is typically 200 nA.

Using innovative design techniques, the ADM7160 provides

superior noise performance for noise-sensitive analog front-end

and RF applications without the need for a noise bypass capacitor.

The ADM7160 is also optimized for use with small 1 µF ceramic

capacitors.

REFERENCE

SHORT-CIRCUIT,

UVLO, AND

THERMAL

PROTECTION

SHUTDOWN

R1

R2

VOUT

VIN

GND

EN

Figure 35. Internal Block Diagram

Internally, the ADM7160 consists of a reference, an error amplifier,

a feedback voltage divider, and a PMOS pass transistor. Output

current is delivered via the PMOS pass device, which is controlled

by the error amplifier. The error amplifier compares the reference

voltage with the feedback voltage from the output and amplifies

the difference. If the feedback voltage is lower than the reference

voltage, the gate of the PMOS device is pulled lower, allowing more

current to pass and increasing the output voltage. If the feedback

voltage is higher than the reference voltage, the gate of the PMOS

device is pulled higher, allowing less current to pass and decreasing

the output voltage.

An internal pull-down resistor on the EN input holds the input

low when the EN pin is left open.

The ADM7160 is available in 16 output voltage options, ranging

from 1.1 V to 3.3 V.

ENABLE FEATURE

The ADM7160 uses the EN pin to enable and disable the VOUT

pin under normal operating conditions. When EN is high, VOUT

turns on; when EN is low, VOUT turns off. For automatic startup,

EN can be tied to VIN.

As shown in Figure 36, when a rising voltage on EN crosses the

active threshold, VOUT turns on. When a falling voltage on EN

crosses the inactive threshold, VOUT turns off. The EN pin has

built-in hysteresis. This hysteresis prevents on/off oscillations that

can occur due to noise on the EN pin as it passes through the

threshold points.

3.0

2.5

2.0

1.5

0.5

1.0

0

0

0.5

1.0

1.5

2.0

2.5

ENABLE VOLTAGE (V)

Figure 36. Typical EN Pin Operation

The EN pin active/inactive thresholds are derived from the VIN

voltage. Therefore, these thresholds vary with changing input

voltage. Figure 37 shows typical EN active/inactive thresholds

when the input voltage varies from 2.2 V to 5.5 V.

1.2

1.0

0.8

0.6

0.2

0.4

0

2.0

2.5

3.0

3.5

4.5

5.0

4.0

5.5

INPUT VOLTAGE (V)

EN ACTIVE

EN INACTIVE

Figure 37. Typical EN Pin Thresholds vs. Input Voltage