RT1025WS datasheet(21/24 Pages) RICHTEK

21 / 24 page

RT1025

is a registered trademark of Richtek Technology Corporation

DS1025-01

July

2022

www.richtek.com

The ECG channel outputs 24 bits of data per channel in

binary twos complement format, MSB first. Bit [23] is

sign bit. A positive full-scale input produces an output

code of 7FFFFFh and the negative full-scale input

produces an output code of 800000h. The output clips

at these codes for signals exceeding full-scale. All 24

bits toggle when the analog input is at positive or

negative full-scale.

ECG

(mV)=ECGACDOutputcode×LSB×1000

ECG Gain

ECGACD Outputcode ×

23 × 1000

ECG Gain

Heartbeat Interval (HBI) Estimation

The RT1025 has a built-in heartbeat interval (HBI)

detector to reduce power consumption of hear-beat

detection. When the signal quality of PPG is good

enough, the BI detector is able to approximate

wavelength of major tone. Instead of complete PPG

signals, only beat time intervals are recorded in SRAM.

The MCU is freed from estimating heart rate; as a

result the amount of data read from the RT1025 SRAM

via I2C/SPI is reduced significantly.

PPG

Average

Reg_HBI

Decision

(Beat Position)

HBI

SRAM

PPG Digital

HBI Digital

Thermal Considerations

The junction temperature should never exceed the

absolute maximum junction temperature TJ(MAX), listed

under Absolute Maximum Ratings, to avoid permanent

damage to the device. The maximum allowable power

dissipation depends on the thermal resistance of the IC

package, the PCB layout, the rate of surrounding

airflow, and the difference between the junction and

ambient

temperatures.

The

maximum

power

dissipation can be calculated using the following

formula :

PD(MAX) = (TJ(MAX) - TA) /

θJA

where TJ(MAX) is the maximum junction temperature,

TA is the ambient temperature, and

θJA is the

junction-to-ambient thermal resistance.

For continuous operation, the maximum operating

junction temperature indicated under Recommended

Operating

Conditions

125°C.

The

junction-to-ambient thermal resistance,

θJA, is highly

package dependent. For a WL-CSP-41B 3.10x3.48

(BS) package, the thermal resistance,

θJA, is 3.75°C/W

standard

JEDEC

51-7

high

effective-thermal-conductivity four-layer test board. The

maximum power dissipation at TA = 25°C can be

calculated as below :

PD(MAX) = (125°C - 25°C) / (3.75°C/W) = 26.6W for a

WL-CSP-41B 3.10x3.48 (BS) package.

The maximum power dissipation depends on the

operating ambient temperature for the fixed TJ(MAX)

and the thermal resistance,

θJA. The derating curves in

Figure 1 allows the designer to see the effect of rising

ambient

temperature

the

maximum

power

dissipation.

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