ACT81460 datasheet(39/60 Pages) ACTIVE-SEMI

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ACT81460

Rev 1.0, 18-Dec-2018

Innovative PowerTM

www.active-semi.com

ActiveSwitcherTM is a trademark of Active-Semi

LOW-DROPOUT LINEAR

REGULATORS

General Description

ACT81460 contains three fully integrated, 100mA, low-

noise, low-dropout linear regulators (LDOs). Each LDO

has been optimized to achieve low quiescent current

under no load conditions. LDO3 can also be configured

in load switch mode to behave like a load switch.

The LDOs require only two small external components

(Cin, Cout) for operation. They ship with default output

voltages that can be modified via the I2C interface for

systems that require advanced power management

functions.

Soft-Start

Each LDO contains a softstart circuit that limits the rate

of change of the output voltage, minimizing input inrush

current and ensuring that the outputs power up mono-

tonically. This circuitry is effective any time the LDO is

enabled, as well as after responding to a short circuit or

other fault condition. The LDO ramp rate is fixed at

1.7V/ms.

Output Voltage Setting

The LDOs regulate to the voltage defined by their I2C

registers LDO1_VSET, LDO2_VSET, and LDO3_VSET.

The LDOs do not have a second VSET register like the

buck converters. They can be programmed between

0.6V and 3.6V in 50mV steps. The following equation

calculates the output voltage based on the LDOx_VSET

VLDOx = 0.6V + LDOx_VSET * 0.050V

Where LDOx_VSET is the decimal equivalent of the

value in each regulator’s I2C LDOx_VSET register.

These registers contain an unsigned 6-bit binary value.

As an example, if LDO1’s LDO1_VSET register con-

tains 11000b (24 decimal), the output voltage is 1.8V.

Active Semi recommends that the LDO’s output voltage

be kept within +/- 25% of the default output voltage to

maintain accuracy. Voltage changes larger than +/- 25%

may require different factory trim settings (new CMI) to

maintain accuracy.

Table 5 shows the output voltage in voltage as a func-

tion of the LDOx_VSET register settings.

LDO Output Voltage (V)

LDOx_VSET [5:3]

000

001

010

011

100

101

110

111

000

0.60

1.00

1.40

1.80

2.20

2.60

3.00

3.40

001

0.65

1.05

1.45

1.85

2.25

2.65

3.05

3.45

010

0.70

1.10

1.50

1.90

2.30

2.70

3.10

3.50

011

0.75

1.15

1.55

1.95

2.35

2.75

3.15

3.55

100

0.80

1.20

1.60

2.00

2.40

2.80

3.20

3.60

101

0.85

1.25

1.65

2.05

2.45

2.85

3.25

3.60

110

0.90

1.30

1.70

2.10

2.50

2.90

3.30

3.60

111

0.95

1.35

1.75

2.15

2.55

2.95

3.35

3.60

Table 5. Vout vs LDOx_VSET Register Setting

Enable / Disable Control

During normal operation, each LDO may be enabled or

disabled via the I2C interface by writing to that regula-

tor's ON bit. Note that disabling an LDO that is used as

an input trigger to another regulator may or may not dis-

able the other regulators following it, depending on the

specific CMI settings. Each LDO has a load discharge

function designed to quickly pull the output voltage to

ground when the LDO is disabled. The circuit connects

an internal resistor (50ohm) from the output to AGND

when the LDO is disabled.

POK and Output Fault Interrupt

Each LDO features a power-OK status bit that can be

read by the system microprocessor via the I2C interface.

If an output voltage is lower than the Power-OK (POK)

threshold, typically 8% below the programmed

regulation voltage, the value of that regulator's POK bit

will be 0.

If a LDO's nFLTMSK bit is set to 1, the ACT81460 will

interrupt the processor if that LDO's output voltage falls

below the Power-OK (POK) threshold. In this case,

nIRQ will assert low and remain asserted until either the

regulator is turned off or back in regulation, and the POK

bit has been read via I2C. After removing the under-

voltage condition, a read operation clears the interrupt.

Overcurrent and Short Circuit Protection

Each LDO provides overcurrent detection and short cir-

cuit protection featuring a current-limit foldback function.

When current limit is reached, the IC can either shut the

output off or limit the output current until the overload

condition is removed. This is controlled by I2C bits

LDOx_ILIM_SHUTDOWN_DIS.

The overcurrent threshold is fixed at 120mA. In both an

overload and a short circuit condition, the LDO limits the

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