ACT5880 datasheet(63/87 Pages) ACTIVE-SEMI

63 / 87 page

ACT5880

Rev 2, 03-Sep-13

- 63 -

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UVLO circuit monitors the voltage at VSYS, it stops

the normal operation when the VVSYS is less than

the VUVLO, reloads registers with default power on

states and starts normal operation when the VVSYS

is greater than VUVLO.

All circuit blocks stop but the always-on VALIVE

output and the RTC circuit keep running when the

system UVLO asserts. The always-on regulator

keeps output even when its output voltage drops,

the RTC keeps running until its input voltage is too

low, the RTCEN bit is reset.

The VVSYS comparator circuit is configurable for

stopping the system as the UVLO function does or

asserting a system voltage low alert when it sees

the VVSYS is less than a programmable threshold.

The threshold is programmed by setting the

SYSLEV[3:0] in a register, refer to the GLOBAL

MAP

and REGISTER AND BIT

DESCRIPTIONS

sections for more details.

Each step-down DC/DCs and the step-up DC/DC

has its own UVLO to assure it only operates when

both its input voltage and the VVSYS are in proper

range.

Over-Current

Each regulator has its own over-current protection.

For step-down DC/DCs and the step-up DC/DC ,

the over-current condition triggers to reduce the

switch frequency to ¼ of normal frequency. In

LDOs, it triggers fold-back current limit. In both

case, the over-current protection consequently

causes the drop of output voltage and so the

house-keeping interrupt assertion if this function is

enabled. Each regulator is safe in unlimited-time

output short-circuit (but not the step-up DC/DC, in

which the rectifier diode might be burned off).

Over-temperature

When the die temperature goes to about 160°C, the

whole circuit of the ACT5880 is shutdown, including

all function blocks, with about 20°C hysteresis when

temperature falls for recovering. This threshold

temperature is higher than functional temperature

thresholds used for other temperature dependent

circuits, including the die-temperature regulation in

charger and the open-drain driver circuit.

House-keeping Oriented Interrupts

There are 14 sources/conditions in 2 types interrupt

oriented for house-keeping, each is programmable

for allowing interrupt or masked.

Table 2 lists the house-keeping oriented interrupt

types. Refer to the INTERRUPT DESCRIPTIONS

section for a summary of all possible interrupts and

the REGISTER AND BIT DESCRIPTIONS section

for more details.

Table 2:

The House-keeping Oriented Interrupts.

INTERRUPT FOR

CONDITIONS

System Voltage low

VVSYS<Voltage set by

SYSLEV[3:0]

Regulator out of

regulation

REG1, REG2, REG3 output 7%

less than normal; REG4 to

REG13 11% less than normal;

REG3 over voltage in constant

current output mode.

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