LP2950

VIN

GND

VDD

CS

SCLK

SDATA

LMT87

VDD

GND

OUT

ADCS747X

1 µF

1 µF

0.1 µF

DSP

Microcontroller

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22

ADCS7476, ADCS7477, ADCS7478

SNAS192G – APRIL 2003 – REVISED MAY 2016

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Product Folder Links: ADCS7476 ADCS7477 ADCS7478

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Copyright © 2003–2016, Texas Instruments Incorporated

8.2 Typical Application

The ADCS747x are monolithic CMOS 12-, 10-, and 8-bit ADCs that use the supply voltage as a reference,

the LMT87, which is a wide range ±0.3°C accurate temperature sensor, is shown in Figure 32.

Figure 32. Typical Application Circuit

8.2.1 Design Requirements

A successful ADCS747x and LMT87 design is constrained by the following factors:

•

8.2.2 Detailed Design Procedure

Designing for an accurate measurement requires careful attention to the timing requirements for the ADCS747x

parts.

Because the ADC747x parts use the supply voltage as a reference, ensuring that the supply voltage is settled to

its final level before exiting the shutdown mode and beginning a conversion is important. After the supply voltage

has settled, the CS is brought to a low level (ideally 0 V) to start a conversion.

Ensuring that any noise on the power supply is less than ½ LSB in amplitude is also important. The supply

voltage must be regarded as a precise voltage reference.

After the CS has been brought low, the user must wait for one complete conversion cycle (approximately 1

μs)

for meaningful data. The dummy conversion cycle is the start-up time of the ADCS747x. The ADCS747x digital

1 LSB of ADCS7476 is 0.805 mV.