9

FN6832.0

January 22, 2009

Block Diagram

Functional Description

ISL9016 contains two high performance LDO’s. High

performance is achieved through a circuit which delivers fast

transient response to varying load conditions. In a quiescent

condition, the ISL9016 adjusts its biasing to achieve the

lowest standby current consumption.

The device also integrates current limit protection, thermal

shutdown protection, reverse current protection and soft-start.

Thermal shutdown protects the device against overheating.

Soft-start limits the start-up input current surges. In some

certain application circuits, the output voltage may be

externally held up, meanwhile, the input voltage could be

connected to ground, or connected to some voltage lower

than the output side, or be left open circuit. ISL9016 features

the reverse current protection; it can limit the current flow from

output to input. This protection will automatically initiate when

Enable Control

The ISL9016 has two separate enable pins, EN1 and EN2,

which independently enable/disable each of the LDO

outputs. When both EN1 and EN2 are low, the whole device

is in shutdown mode. In this condition, all on-chip circuits are

off, and the device draws minimum current, typically less

than 0.1mA. When one or both the EN pins go high, the

LDO1 and/or LDO2 will be enabled accordingly based on the

voltage signal applied on its related EN pin and start from the

soft-start. Likewise, when one or both EN pins go low, LDO1

and/or LDO2 will be disabled based on the signal applied on

its related EN pin. A 100k

Ω (or above) pull-up resistor should

be connected between ENx pin and the external control

voltage (as shown in the “Typical Application Diagram” on

page 8).

LDO Protections

ISL9016 offers several protections which make it ideal for

using in battery-powered application circuits.

ISL9016 provides short-circuit protection by limiting the

output current to typical 265mA. When short circuit happens,

the circuit is limited at 265mA (typical). If the short circuit

lasts long enough, the die temperature increases, and the

over-temperature protection circuit will turn off the output.

When the die temperature reaches about +145°C, the thermal

protection starts working. Under the overheat condition, only

the LDO sourcing more than 50mA will be shut off. This does

not affect the operation of the other LDO. If both LDOs source

more than 50mA and an overheat condition occurs, both LDO

outputs will be disabled. Once the die temperature falls back

to about +110°C, the disabled LDO(s) are re-enabled and

soft-start automatically takes place.

In certain applications, the following input/output situations

may occur:

CONTROL

LOGIC

SHORT CIRCUIT

THERMAL PROTECTION

SOFT-START

UNDERVOLTAGE

LOCKOUT

BANDGAP

TEMP-SENSOR

REFERENCE

VOLTAGES

VREF1

VREF2

VREF3

VOUT1

EN1

+

VIN

VIN

EN1

EN2

VOUT2

VOUT1

GND

VREF1

REVERSE CURRENT

PROTECTION

LDO-2

LDO-1

ISL9016