ACT8600 datasheet(40/51 Pages) ACTIVE-SEMI

40 / 51 page

ACT8600

Rev 3, 15-Nov-12

Innovative Power

ActivePMU

TM and ActivePathTM are trademarks of Active-Semi.

2CTM is a trademark of NXP.

- 40 -

www.active-semi.com

General Description

The REG5, REG6, REG7 and REG8 are low-noise,

low-dropout linear regulators (LDOs) that are

optimized for low noise and high-PSRR operation.

LDO Output Voltage Programming

The REG5, REG6, REG7 and REG8 feature

independently-programmable output voltages that

are set via the I2C serial interface, increasing

flexibility while reducing total solution and size and

cost. Set the output voltage by writing to the LDO’s

VSET[ ] register. Each LDO’s VSET[ ] register

provides the following output voltage options as

shown in Table 5.

In order to ensure safe operation under over-load

conditions, each LDO features current-limit circuitry

with current fold-back. The current-limit the current

that can be drawn from the output, providing

protection in overload conditions. For additional

protection under extreme over current conditions,

current-fold-back protection reduces the current-

limit by approximately 50% under extreme overload

conditions.

Enabling and Disabling the LDOs

All LDOs feature independent enable/disable

control via the I2C serial interface. Independently

enable or disable each output by writing to the

appropriate ON[ ] bit.

Power-OK

The REG5, REG6, REG7 and REG8 feature a

power-OK status bit (OK[ ]) that can be read by the

system microprocessor via the I2C interface. If an

output voltage is lower than the power-OK

threshold, typically 11% below the programmed

regulation voltage, this bit clears to 0.

Interrupts

Each LDO may optionally interrupt the processor if

its output voltage falls out of regulation. Enable

interrupts by setting a regulator’s nFLTMSK[ ] bit.

Optional LDO Output Discharge

The REG5, REG6, REG7 and REG8 feature

optional output voltage discharge. When this

feature is enabled, the LDO output is discharged to

ground through a 1.5kΩ resistance when the LDO is

shutdown. This feature may be enabled or disabled

via the I2C interface by writing to an LDO’s DIS[ ]

bit.

Output Capacitor Selection

The REG5, REG6, REG7 and REG8 require just a

small 2.2uF ceramic capacitor for stability. For best

performance, each output capacitor should be

connected directly between each output and

ground, with a short and direct connection. High

quality ceramic capacitors such as X7R and X5R

dielectric types are strongly recommended.

Backup Battery Charger

REG9 is always-on and REG10 is low-dropout

linear regulators (LDO). They both feature low-

quiescent

supply

current,

and

current-limit

protection, and are ideally suited for always-on

power supply applications, such as for a real-time

clock, or as a backup-battery or super-cap charger.

REG9 features internal circuitry that limits the

reverse supply current to less than 1uA when the

input voltage falls below the output voltage, as can

encountered

backup-battery

charging

applications. REG9 internal circuitry monitors the

input and the output, and disconnects internal

circuitry and parasitic diodes when the input voltage

falls below the output voltage, greatly minimizing

backup battery discharge. The always-ON LDOs

also feature a constant current-limit, which protects

the IC under output short-circuit conditions as well

as provides a constant charge current. When

operating as a backup battery charger.

Figure 3:

Always ON LDO

LOW-DROPOUT LINEAR REGULATORS

ACT8600 Datasheet(PDF) 40 Page - Active-Semi, Inc

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