ACT5880
Rev 2, 03-Sep-13
LOW-NOISE, LOW-DROPOUT LINEAR REGULATORS
General Description
Output Current Limit
There are total 13 low drop-out linear regulators in
the ACT5880. Except for the one for backup battery
charger and the always-on LDO, the rest 11 LDOs
have similar way to control and to program through
the access of sets of registers, but the one tied for
REG2 has an additional control access though a
joint manipulation. Refer to Table 5 for a quick
summary of output currents and default output
voltages for each LDOs.
Each LDO contains current-limit circuitry featuring a
current-limit fold-back function. During normal and
moderate overload conditions, the regulators can
support more than their rated output currents.
During extreme overload conditions, however, the
current limit is reduced by approximately 30%,
reducing power dissipation within the IC.
Configuration Options
Output Voltage Programming
Table 5
By default, each LDO powers up and regulates to
its default output voltage. Once the system is
enabled, each output voltage may be independently
programmed to a different value by writing to the
regulator's VSET[-] register via the I2C serial
interface as shown in the STEP-DOWN DC/DC
and LDO OUTPUT VOLTAGE SETTING table.
The Key Specifications of LDOs.
MAXIMUM
OUTPUT
(mA)
DEFAULT DEFAULT
STATUS OUTPUT(V)
NAME
REG4
ON
2.9
360
REG5
REG6
REG7
REG8
REG9
REG10
ON
OFF
ON
2.9
2.9
3.0
2.5
1.2
3.3
250
360
360
360
250
150
Enable / Disable Control
During normal operation, each LDO may be
enabled or disabled via the I2C interface by writing
to that LDO's ON[ ] bit. To enable the LDO set ON[ ]
to 1, to disable the LDO clear ON[ ] to 0.
ON
OFF
ON
Output Discharge
Each of the ACT5880’s LDOs features an optional
output discharge function, which discharges the
output to ground through a 1kꢀ resistance when the
LDO is disabled. This feature may be enabled or
disabled by setting DIS[-] via; set DIS[-] to 1 to
enable this function, clear DIS[-] to 0 to disable it.
REG11
REG12
REG13
OFF
OFF
OFF
1.8
1.8
2.8
80
250
150
LDO tied in
REG2
OFF
1.8
10
Low-Power Mode
Backup Battery
Charger
ON
ON
2.7
1.8
5
Each of ACT5880's LDOs features a LOWIQ[-] bit
which, when set to 1, reduces the LDO's quiescent
current by about 30%, saving power and extending
battery lifetime.
Always-on LDO
3.5
The OUT6 and the OUT9 also have pin control
inputs for controlling their on/off together with the
on/off bit controls through the register access.
When both the ON bit and ON pin input are used for
control, the later change takes effect. Upon the
power up, if the default of ON bit is different than
the ON pin input, the OUT is ON. In other words,
the OUT upon power on is off only both the ON bit
and ON pin input are set for off. This arbitration is
enough and does well to most cases. However, if
one input sets the OUT to have a status that it
already outputs for in the condition that the OUT
sets for the complementary status by other input,
the input should send out a toggle, instead of repeat
the same logic volume.
OK[ ] and Output Fault Interrupt
Each LDO features a power-OK status bit that can
be read by the system microprocessor via the
interface. If an output voltage is lower than the
power-OK threshold, typically 7% below the
programmed regulation voltage, the value of that
regulator's OK[-] bit will be 0.
If a LDO's nFLTMSK[-] bit is set to 1, the ACT5880
will interrupt the processor if that LDO's output
voltage falls below the power-OK threshold. In this
case, nIRQ will assert low and remain asserted until
the OK[-] bit has been read via I2C.
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