Data Sheet

ADP1606/ADP1607

This current-mode PWM regulation system allows fast

transient response and tight output voltage regulation. PWM

mode operation results in lower efficiencies than PFM mode at

light loads.

Auto Mode

Auto mode is a power saving feature that forces the auto mode

version of the ADP1607 and the auto mode of the ADP1606 to

switch between PFM and PWM in response to output load

changes. In auto mode, the ADP1606/ADP1607 operate in PFM

mode for light load currents and switch to PWM mode for

medium and heavy load currents.

PFM Mode

When the auto mode version of the ADP1607 and the auto

mode of the ADP1606 are operating under light load

conditions, the effective switching frequency and supply current

are decreased and varied using PFM to regulate the output

voltage. This results in improved efficiencies and lower

quiescent currents. In PFM mode, the converter only switches

when necessary to keep the output voltage between the PFM

comparator high output voltage threshold and the lower sleep

mode exit voltage threshold. Switching stops when the upper

PFM limit is reached and resumes when the lower sleep mode

exit threshold is reached.

and the device enters sleep mode. In sleep mode, the

ADP1606/ADP1607 are mostly shut down, significantly

reducing the quiescent current. The output voltage is

discharged by the load until the output voltage reaches the

lower sleep mode exit threshold. After crossing the lower sleep

mode exit threshold, switching resumes and the process repeats.

Mode Transition

The auto mode version of the ADP1607 and the auto mode of

the ADP1606 switch automatically between PFM and PWM

modes to maintain optimal efficiency. Switching to PFM allows

the converter to save power by supplying the lighter load

current with fewer switching cycles. The mode transition point

depends on the operating conditions. See Figure 16 for typical

transition point to prevent instability and decreased efficiencies

that may result if the converter oscillates between PFM and

PWM for a fixed input voltage and load current.

The output voltage in PWM can be greater than or less than the

PFM voltage of that device.

INTERNAL CONTROL FEATURES

Input to Output Isolation

While in shutdown, the ADP1606/ADP1607 manage the

voltage of the bulk of the PMOS to force it off and internally

isolate the path from the input to output. This isolation allows

the output to drop to ground, reducing the current

consumption of the application in shutdown.

Soft Start

The ADP1606/ADP1607 soft start sequence is designed for

optimal control of the device. When EN goes high, or when the

device recovers from a TSD, the start-up sequence begins. The

output voltage increases through a sequence of stages to ensure

that the internal circuitry is powered up in the correct order as

the output voltage rises to its final value.

Current Limit

The ADP1606/ADP1607 are designed with a fixed 1 A typical

current limit that does not vary with duty cycle.

Synchronous Rectification

In addition to the N-channel MOSFET switch, the

ADP1606/ADP1607 have a P-channel MOSFET switch to build

the synchronous rectifier. The synchronous rectifier improves

efficiency, especially for heavy load currents, and reduces cost

and board space by eliminating the need for an external

Schottky diode.

Compensation

The PWM control loop of the ADP1606/ADP1607 is internally

compensated to deliver maximum performance with no

additional external components. The ADP1606/ADP1607 are

designed to work with 2.2 μH chip inductors and 10 μF ceramic

capacitors. Other values may reduce performance and/or

stability.

TSD Protection

The ADP1606/ADP1607 include TSD protection when the

device is in PWM mode only. If the die temperature exceeds

150°C (typical), the TSD protection activates and turns off the

power devices. They remain off until the die temperature falls

below 135°C (typical), at which point the converter restarts.

Rev. D | Page 11 of 16