APW8855 Datasheet, PDF (32/43 Pages) Anpec Electronics Coropration – High Current, High Frequency 7 Outputs Voltage Regulator and Power Management IC for High Performance Tablet and Ultra Notebook Applications

APW8855
15.1 VR Function Description(Cont.)
POK Output
The POK circuitry monitors the VR1-VR5 via the FB pins of each regulator to make sure that the output of each
regulator has reached its desired set point during the start up. When all these voltages have reached 90% of their set
point, then POK will switch from a low state to high after a 1 ms delay time. The POK pin is an open drain output that
will switch high via an external pull up resistor. It can be pulled up to a maximum voltage of up to 5.5V.
The POK also monitors the FB voltage for any over voltage that may happen during the operation. This threshold is
typically set at 130% of the desired set point. If any of the voltages exceeds this threshold and satisfied the blanking
time the POK switches low and after a short delay of about 2usec or so, the outputs latch off and system returns to G3
state.
During the power down or at any point either of these VR1-VR5, output voltages drop below 90% typical set point and
continue over blanking time, the POK pin switches to low state again.
15.2 I2C Function Description
I2C Overview
APW8855 is a slave-only device that is mastered by the SoC. It resides off the SoC’s I2C. The slave device imple-
mented on APW8855 side is an asynchronous implementation and will support the high speed mode (3.4MHz).
Some of the main features for the I2C slave are:
• APW8855 is accessed using a 7-bit addressing scheme.
• I2C slave is not allowed to stretch the clock, and must be capable of being multi-mastered in a debug
environment.
• The interface draws as minimum power when not actively reading/writing registers.
• The slave adapts to the incoming frequency without any communication as the protocol for fast mode and
high speed mode is the same.
• Interface implementation is asynchronous.
Slave Address
APW8855 supports the standard I2C read and write functions. The configuration register space is divided to 59-byte
partitions. APW8855 supports five 7-bit device addresses to access each of the 59 byte partitions.
Slave Address
11 0111 0
Table 5. I2C Slave Addresses
The slave addresses need to be locked in order to avoid that software can overwrite them and disable the
communication.
Copyright © ANPEC Electronics Corp.
32
Rev. A.1 - Dec., 2015
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