TMS370 datasheet(52/59 Pages) TI

52 / 59 page

TMS370Cx7x

8-BIT MICROCONTROLLER

SPNS034C – SEPTEMBER 1995 – REVISED FEBRUARY 1997

POST OFFICE BOX 1443

• HOUSTON, TEXAS 77251–1443

analog-to-digital converter 1 (ADC1)

The ADC1 has a separate power bus for its analog circuitry. These pins are referred to as VCC3 and VSS3. The

purpose is to enhance ADC1 performance by preventing digital switching noise in the logic circuitry that can

be present on VSS1 and VCC1 when coupling into the A/D analog stage. All ADC1 specifications are given with

respect to VSS3 unless otherwise noted.

Resolution

8-bits (256 values)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Monotonic

Yes

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Output conversion mode

00h to FFh (00 for VI ≤ VSS3 ≤; FF for VI ≤ Vref)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Conversion time (excluding sample time)

164 tc

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

recommended operating conditions

MIN

NOM

MAX

UNIT

VCC3 Analog supply voltage

4.5

5.5

VCC3 Analog supply voltage

VCC1–0.3

VCC1+0.3

VSS3

Analog ground

VSS1–0.3

VSS1+0.3

Vref

Non-VCC3 reference†

2.5

VCC3

VCC3 + 0.1

Analog input for conversion

VSS3

Vref

† Vref must be stable, within ± 1/2 LSB of the required resolution, during the entire conversion time.

operating characteristics over recommended ranges of operating conditions

PARAMETER

TEST CONDITIONS

MIN

MAX

UNIT

Absolute accuracy‡

VCC3 = 5.5 V

Vrerf = 5.1 V

±1.5

LSB

Differential/integral linearity error‡§

VCC3 = 5.5 V

Vrerf = 5.1 V

±0.9

LSB

ICC3

Analog supply current

Converting

ICC3

Analog supply current

Nonconverting

µA

Input current, AN0 – AN7

0 V

≤ VI ≤ 5.5 V

µA

Iref

Input charge current

Z f

Source impedance of V f

SYSCLK

≤ 3 MHz

Ω

Zref

Source impedance of Vref

3 MHz < SYSCLK

≤ 5 MHz

Ω

‡ Absolute resolution = 20 mV. At Vref = 5 V, this is one LSB. As Vref decreases, LSB size decreases; therefore, the absolute accuracy and

differential/integral linearity errors in terms of LSBs increase.

§ Excluding quantization error of 1/2 LSB

TMS370 Datasheet(PDF) 52 Page - Texas Instruments

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