stled325 STMicroelectronics, stled325 Datasheet - Page 27

• Manufacturer Part Number: stled325
• Description: I?c Interfaced, Advanced Led Controller/driver With Keyscan, Standby Power Management And Real Time Clock Rtc
• Manufacturer: STMicroelectronics

STLED325
3.14
3.15
3.16
3.17
While the interrupt is being read by the MCU and a new GPIO or key data comes in, no new
interrupt is generated but the register for GPIO and KEY data is updated so that the MCU
does not miss the new KEY and GPIO data.
Ready
The STLED325 supports cutting-off power to the main board for standby operation for good
power management. STBY will be set to high when the READY transitions from high to low.
During a cold boot up or wake up from standby, if the READY pin stays low, the STLED325
will assert the STBY when the guard timer has finished counting down to 0.
When the READY drops to a low, MUTE goes high immediately and soon after (2µs
minimum) the STBY is asserted.
In the normal mode of operation, when READY is a high, the STBY is asserted only when
the guard timer is enabled and has finished counting down to 0. This is meant to put the
system into stand-by as the READY pin was stuck at high and the guard timer register was
not cleared before it finished counting down to 0. It is advised to disable the guard timer
during normal operation.
Mute
The MUTE pin will be set to logic high to mute the audio output before power is cut to the
host processor. In wake up mode, the MUTE pin will be set to logic low to enable the audio
output immediately after the high assertion of the READY pin. In general, MUTE follows
READY pin with an inverted polarity. This pin is used to prevent pop-up sound during power-
up and power-down states.
GPIO
The STLED325 supports 2 additional GPIOs that can be configured as inputs or outputs. As
an input, the GPIO can be used to interface to a sensor or a switch or key and as an output,
the GPIO can be used to drive individual indicator LEDs.
Power sense circuits
The STLED325 has a built-in power sense circuit which detects power failures and
automatically switches to the battery or super-cap supply when a power failure occurs. The
energy needed to sustain the SRAM and clock operations can be supplied by small lithium
button supply or a super-cap when a power failure occurs. When operating from the battery
or super-cap, all the inputs and outputs are driven to a known state (generally L).
Doc ID 17576 Rev 1
Functional description
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