ACT8849 datasheet(27/35 Pages) ACTIVE-SEMI

27 / 35 page

ACT8849

Rev PrB, 12-Jun-14

Innovative PowerTM

- 27 -

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TM is a trademark of Active-Semi.

I2CTM is a trademark of NXP.

Control Signals

Enable Inputs

The ACT8849 features a variety of control inputs,

which are used to enable and disable outputs

depending upon the desired mode of operation.

PWREN, PWRHLD are logic inputs, while nPBIN is

a unique, multi-function input.

nPBIN Multi-Function Input

The ACT8849 features the nPBIN multi-function

pin, which combines system enable/disable control

with a hardware reset function. Select either of the

two pin functions by asserting this pin, either

through a direct connection to GA, or through a

50kΩ resistor to GA, as shown in Figure 2.

Manual Reset Function

The second major function of the nPBIN input is to

provide a manual-reset input for the processor. To

manually-reset the processor, drive nPBIN directly

to GA through a low impedance (less than 2.5kΩ).

An internal timer detects the duration of the MR

event:

If the MR is asserted for more than 4s, ACT8849

commences a power cycle routine in which case all

regulators are turned off and then turned back on. A

status bit, PCSTAT[ ], is set after the power cycle.

The PCSTAT[ ] bit is automatically cleared to 0 after

read.

Figure 2:

nPBIN Input

nPBSTAT Output

nPBSTAT is an open-drain output that reflects the

state of the nPBIN input; nPBSTAT is asserted low

whenever nPBIN is asserted, and is high-Z

otherwise. This output is typically used as an

interrupt signal to the processor, to initiate a

software-programmable routine such as operating

mode selection or to open a menu. Connect

nPBSTAT to an appropriate supply voltage through

a 10kΩ or greater resistor.

nIRQ Output

nIRQ is an open-drain output that asserts low any

time an interrupt is generated. Connect a 10kΩ or

greater pull-up resistor from nIRQ to an appropriate

voltage supply. nIRQ is typically used to drive the

interrupt input of the system processor.

Many of the ACT8849's functions support interrupt-

generation as a result of various conditions. These

are typically masked by default, but may be

unmasked via the I

2C interface. For more

information about the available fault conditions,

refer to the appropriate sections of this datasheet.

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