ADP5135

Data Sheet

Rev. 0 | Page 14 of 24

Regulator output voltages are set through external resistor

dividers or can be optionally factory programmed to default

values (see the Ordering Guide section).

When a regulator is turned on, the output voltage ramp rate is

controlled through a soft start circuit to avoid a large inrush

current caused by the charging of the output capacitors.

Power-Good Output

Power-good outputs are available for each buck channel to

monitor their respective output voltages. The PGx pin connects

to a pull-up current to drive external regulators or other

circuits. In this configuration, the PGx pin goes high when the

channel being monitored is in regulation and goes low when the

output voltage falls below 85% of the nominal VOUTx level.

The PGx pin can also drive an LED for fault monitoring. In this

configuration, a red LED, for example, is biased and current

sinks into the PGx pin when the output voltage falls below 85%

of the nominal VOUTx level, thereby turning the LED on, and

turns off when the output voltage is in regulation.

Thermal Protection

In the event that the junction temperature rises above 150°C,

the thermal shutdown circuit turns off all the regulators. Extreme

junction temperatures can be the result of high current opera-

tion, poor circuit board design, or high ambient temperature.

A 20°C hysteresis is included so that when thermal shutdown

occurs, the regulators do not return to operation until the on-chip

temperature drops below 130°C. When coming out of thermal

shutdown, all regulators restart with soft start control.

Undervoltage Lockout

To protect against battery discharge, undervoltage lockout

(UVLO) circuitry is integrated into the system. If the input

voltage on AVIN drops below the UVLO threshold, 2.45 V

minimum, all channels shut down. In the buck channels, both

the power switch and the synchronous rectifier turn off. When

the voltage on AVIN rises above the UVLO threshold, the

device is enabled once more.

Alternatively, the user can request a new device model with a

UVLO set at a higher level, suitable for 5 V supply applications,

or to a lower level, suitable for low voltage operations. To order

a device with options other than the default options listed in the

Ordering Guide section, contact your local Analog Devices,

Inc., sales or distribution representative.

In case of a thermal or UVLO event, the active pull-downs (if

factory enabled) are enabled to quickly discharge the output

capacitors. The pull-down resistors remain engaged until the

thermal fault event is no longer present or when the input

supply voltage falls below the power-on reset voltage level

Precision Enable and Shutdown Control

The ADP5135 has an individual enable control pin for each

puts the device out of shutdown and turns on the housekeeping

mode. In this mode, the current consumption of the device

drops to below 1.5 μA.

Figure 36 shows the activation timings for the ADP5135 when

good signals (PGx) monitoring all regulators.