MCP4822E-SN Datasheet, PDF(29/46 Page) Microchip Technology – 8/10/12-Bit Dual Voltage Output Digital-to-Analog Converter with Internal VREF and SPI Interface

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MCP4822E-SN Datasheet, PDF (29/46 Pages) Microchip Technology – 8/10/12-Bit Dual Voltage Output Digital-to-Analog Converter with Internal VREF and SPI Interface

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MCP4802/4812/4822

6.7 Selectable Gain and

Offset Bipolar Voltage Output

Using a Dual Output DAC

In some applications, precision digital control of the

output range is desirable. Example 6-4 illustrates how

to use the MCP4802/4812/4822 family of devices to

achieve this in a bipolar or single-supply application.

This circuit is typically used for linearizing a sensor

whose slope and offset varies.

The equation to design a bipolar âwindowâ DAC would

be utilized if R3, R4 and R5 are populated.

EXAMPLE 6-4:

BIPOLAR VOLTAGE SOURCE WITH SELECTABLE GAIN AND OFFSET

VDD

VCC+

VOUTA

DACA

Dual Output DAC:

MCP4802

(DACA for Gain Adjust)

VDD

VCC+

MCP4812

MCP4822

DACB

VOUTB

VIN+

SPI

(DACB for Offset Adjust)

R4 0.1 ÂµF

VCCâ

VOUTA = 2.048 ï GA ï D-2---N-n-

VCCâ

VOUTB = 2.048 ï GB ï D-2---N-n-

VIN+ = V----O----U----T---BR---R-3---4-+---+---R--V-4---C---C------R----3-

G = Gain selection (1x or 2x)

N = DAC bit resolution

DA , DB = Digital value of DAC (0-255) for MCP4802

= Digital value of DAC (0-1023) for MCP4812

= Digital value of DAC (0-4095) for MCP4822

VIN+

ï¦

ï¨

RR----21-ï¸ï¶

VOUT

ï¦

ï¨

RR----21-ï¸ï¶

Offset Adjust Gain Adjust

Thevenin

Equivalent

Bipolar âWindowâ DAC using R4 and R5

V45 = V----C---C----+--R-R---4-4---+-+-----RV---5-C---C------R----5-

R45 = R----R4----4+--R----R5----5

VIN+ = V----O----U----T--R-B---3R----+4--5---R-+---4--5-V----4--5---R----3

VIN+ï¨ï¦1 + RR----21-ï¸ï¶

ï¦

Aï¨

RR----21-ï¸ï¶

Offset Adjust Gain Adjust

ï£ 2010 Microchip Technology Inc.

DS22249A-page 29

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