TPS8804 datasheet(21/48 Pages) TI1

21 / 48 page

COSWRI=1

COSWRG=1

VINT

COO

CON

COP

To A MUX

COSWRO=1

10 k -

100 k

Sen sor

Working

Counter

0.22 …F

100 k

PREF

RI=1 k

RI=100 k

COSWREF=1

VINT

COTEST_DIR

COTEST_EN

COREF[1:0]

To P hoto A mp

COAMP_EN

200 k

PREF_SEL=0

PREF_SEL=1

VINT

To MCU G PIO

TPS8804

www.ti.com

SLVSF29 – OCTOBER 2019

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7.3.3.2 LED Voltage Supply

Enough voltage must be provided to the LED such that the DINA voltage is at least the dropout voltage

(VDINA,DROP) above the CSA voltage while the LED driver is enabled. The DINA voltage must not exceed 11.5V.

Because of the high LED drive currents, a large capacitor connected to the LED anode is required to provide

pulsed power to the LED. Any supply meeting the voltage requirements can be used to charge the LED

capacitor. Connect the LED anode to LEDLDO when VCC > 11.5 V.

The LED LDO clamps the VSLC voltage and blocks reverse current with an integrated diode. It is current limited

to prevent inrush current caused by charging the large capacitor. The regulation voltage is adjustable in the

LEDLDO register. The LED LDO may be operated with VSLC below the regulation voltage. In this case, the

LEDLDO voltage will stabilize to VSLC minus a diode voltage drop.

7.3.4 Carbon Monoxide Sensor AFE

Figure 4. Carbon Monoxide Detection Circuit

The TPS8804 CO AFE connects to an electrochemical CO sensor. The amplifier converts the microamps of

sensor current into a voltage readable by an ADC. This is achieved with a low-offset, low-power op-amp with

configurable input, gain, and output resistors.

TPS8804 데이터시트(PDF) 21 Page - Texas Instruments

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