RT1025

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DS1025-01

July

2022

18

Interrupts

To facilitate MCU programming and sensor data flow control, the RT1025 supports various interrupts for each

function. The INT_CON register enables or disables interrupts on various events. Host MCU can identify the exact

cause of interrupt by reading the INT_STATUS register. Below table lists supported interrupts and their usage.

Interrupt

Description

SRAM_ECG

ECG SRAM threshold level is reached

SRAM_ECG_WFULL

ECG SRAM is full.

SRAM_ECG_REMPTY

ECG SRAM is empty

SRAM_PPG1

PPG1 SRAM threshold level is reached

SRAM_PPG1_WFULL

PPG1 SRAM is full

SRAM_PPG1_REMPTY

PPG1 SRAM is empty

SRAM_PPG2

PPG2 SRAM threshold level is reached

SRAM_PPG2_WFULL

PPG2 SRAM is full

SRAM_PPG2_REMPTY

PPG2 SRAM is empty

SRAM_HBI

HBI SRAM threshold level is reached

SRAM_HBI_WFULL

HBI SRAM is full

SRAM_HBI_REMPTY

HBI SRAM is empty

PPG Channel

The LED driver and the external voltage boost are used

to light up the external LED. The LED full scale current

range is from 10mA to 105mA with a 3-bit current step

of 15mA via DAC register setting. Push-Pull mode and

H-Bridge mode of the LED driver schemes are

supported. Suggest to use Push-Pull LED driving

configuration as shown in below figure. The minimum

external

supply

voltage

(LED_SUP)

=

0.7V

+

(maximum voltage drop across the LED).

LED DRV

TX1

TX2

LED SUP

Boost

LED DRV

TX1

TX2

Push-Pull Mode

H-Bridge Mode

LED SUP

Boost

PPG Channel - Receiver Front-End

As shown in the block diagram for PPG acquisition, the

photo detector transfers the reflected light into current

and then amplifies by TIA that converts the input

photodiode

current

into

an

appropriate

voltage.

TIA_Filter was controlled by the register for the input

current low pass filter tuning. PGA_Gain was used to

set the PGA Gain. AMB_DAC control the current

source to cancel the ambient light leakage from photo

detector. The AMB_DAC has a cancellation current

range of 6

µA with six steps (1µA each) for two phases

(LED1/LED2 phase and AMB1/AMB2 phase). The