ACT8870 datasheet(21/38 Pages) ACTIVE-SEMI

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ACT8870QJ-T

REV 0 23-DEC-2016

Innovative PowerTM

ActiveSwitcherTM is a trademark of Active-Semi.

SYSTEM CONTROL INFORMATION

General

The ACT8870 is a single-chip integrated power man-

agement solution designed to power many processors

such as the Atmel SAMA5D3. It integrates four highly

efficient buck regulators, three LDOs, and an integrated

load bypass switch. Its high integration and high switch-

ing frequency result in an extremely small footprint and

lost power solution. It contains a master controller that

manages startup sequencing, timing, voltages, slew

rates, sleep states, and fault conditions. I2C configura-

bility allows system level changes without the need for

costly PCB changes. The built-in load bypass switch en-

ables full sequencing configurability in 3.3V systems.

The ACT8870 master controller monitors all outputs and

reports faults via I2C and hardwired status signals.

Faults can masked and fault levels and responses are

configurable via I2C.

Many of the ACT8870 pins and functions are configura-

ble. The IC’s default functionality is defined by the de-

fault CMI (Code Matrix Index), but much of this function-

ality can be changed via I2C. The first part of the

datasheet describes basic IC functionality and default

pin functions. The end of the datasheet provides the

configuration and functionality specific to each CMI ver-

sion. Contact sales@active-semi.com for additional in-

formation about other configurations.

I2C Serial Interface

To ensure compatibility with a wide range of systems,

the ACT8870 uses standard I2C commands. The

ACT8870 operates as a slave device, and is addressed

using a 7-bit slave address of 0x5Ah followed by an

eighth bit, which indicates whether the transaction is a

read-operation or a write-operation 1011010x. “x” is a 0

for write operation and 1 for a read operation. Use ad-

dress 0xB4h for write operations and 0xB5h for read op-

erations.

There is no timeout function in the I2C packet pro-

cessing state machine, however, any time the I2C state

machine receives a start bit command, it immediately

resets the packet processing, even if it is in the middle

of a valid packet.

The ACT8870 holds the I2C state machine in reset dur-

ing the RESET, Idle, OVUVFLT, and THERMAL states

to avoid a corruption of registers when the voltage reg-

ulators are out of spec.

I2C commands are communicated using the SCL and

SDA pins. SCL is the I2C serial clock input. SDA is the

data input and output. SDA is open drain and must have

a pullup resistor. Signals on these pins must meet timing

requirements in the Electrical Characteristics Table.

I2C Registers

The ACT8870 contains an array of internal registers

contain the IC’s basic instructions for setting up the IC

configuration, output voltages, sequencing, fault

thresholds, fault masks, etc. These registers are what

give the IC its operating flexibility. The two types of

registers are described below.

Basic Volatile – These are R/W (Read and Write) and

RO (Read only). After the IC is powered, the user can

modify the R/W register values to change IC

functionality. Changes in functionality include things like

masking certain faults. The RO registers communicate

IC status such as fault conditions. Any changes to these

registers are lost when power is recycled. The default

values are fixed and cannot be changed by the factory

or the end user.

Basic Non-Volatile – These are R/W and RO. After the

IC is powered, the user can modify the R/W register

values to change IC functionality. Changes in

functionality include things like output voltage settings,

startup delay time, and current limit thresholds. Any

changes to these registers are lost when power is

recycled. The default values can be modified at the

factory to optimize IC functionality for specific

applications. Please consult sales@active-semi.com for

custom options and minimum order quantities.

When modifying only certain bits within a register, take

care

not

inadvertently

change

other

bits.

Inadvertently changing register contents can lead to

unexpected device behavior.

State Machine

The ACT8870 contains an internal state machine with

five internal states.

RESET State

In the RESET, or “cold” state, the ACT8870 is waiting

for the input voltage on VIN to be within a valid range

defined by I2C bits POK_OV_SET and POK_UV_SET.

All regulators are off in RESET. nRESET, nRE-

SET_AUX1, and nRESET_AUX2 are asserted low. All

volatile registers are reset to defaults and Non-Volatile

registers are reset to programmed defaults. The IC tran-

sitions from RESET to ACTIVE when the input voltage

enters the valid range. The IC transitions from any other

state to RESET if the input voltage drops below the

UVLO threshold voltage.

ACTIVE State

The ACTIVE state is the normal operating state when

the input voltage is within the allowable range, all out-

puts are turned on, and no faults are present. When en-

tering the ACTIVE state from the RESET state, all reg-

ulators are powered on following their programmed

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