RT1025

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is a registered trademark of Richtek Technology Corporation

www.richtek.com

DS1025-01

July

2022

12

Power on Sequence

Below figure shows the power on sequence for the device supply voltage and control signals.

I2C/SPI command

PPG External Boost

Voltage

AFE_PWD

RESETB

AVDD_HV

AVDD28

DVDDIO

DVDD18

Power ON

Active

Idle

Active

Power OFF

5ms

45ms

5ms

45ms

Note

Note

Note : Settling time of the PPG external boost voltage source

SPI / I2C Interface

The RT1025 device contains both I2C slave and SPI slave interfaces which share some pins. Only one of the

interface can be operated after the device completes POR or a hard reset. I2C interface supports fast mode (bit rate

up to 400kB/s). SPI interface operate at 2MHz. I2C or SPI interface was selected by pin I2C_SEL (B4). The I2C

device address depends upon the state of pin SPI_MOSI (E2) during power-up as shown in the table below.

I/O Pin

I2C_SEL (B4)

SPI_MOSI (E2)

Reg 7-bit Address

Reg 7-bit Address

Reg_0

Reg_1

I2C

Logic High

Logic High

0x37

0x27

Logic Low

0x33

0x23

SPI

Logic Low

SPI slave input

0x33

0x23

I2C Interface

The I2C slave interface operates at a maximum speed of 400KHz in I2C “Fast Mode”. The SDA (data) is an Active

drive/wired-and, bi-directional pin and the SCL (clock) is an input pin. The device always operates as an I2C slave

and only uses 7-bit addressing.