AD7243A 查看數據表（PDF） - Analog Devices

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AD7243A

LC2MOS 12-Bit Serial DACPORT

Analog Devices 

AD7243

TERMINOLOGY

Bipolar Zero Error

Bipolar Zero Error is the voltage measured at VOUT when the

DAC is configured for bipolar output and loaded with all 0s

(Two’s Complement Coding) or with 1000 0000 0000 (Offset

Binary Coding). It is due to a combination of offset errors in the

DAC, amplifier and mismatch between the internal gain resis-

tors around the amplifier.

Full-Scale Error

Full-Scale Error is a measure of the output error when the am-

plifier output is at full scale (for the bipolar output range full

scale is either positive or negative full scale). It is measured with

respect to the reference input voltage and includes the offset

errors.

Digital-to-Analog Glitch Impulse

This is the voltage spike that appears at VOUT when the digital

code in the DAC latch changes, before the output settles to its

final value. The energy in the glitch is specified in nV secs, and

is measured for an all codes change from 0000 0000 0000 to

1111 1111 1111 and vice versa.

Digital Feedthrough

This is a measure of the voltage spike that appears on VOUT as a

result of feedthrough from the digital inputs on the AD7243. It

is measured with LDAC held high.

Relative Accuracy (Linearity)

Relative Accuracy, or endpoint linearity, is a measure of the

maximum deviation of the DAC transfer function from a

straight line passing through the endpoints of the transfer func-

tion. It is measured after allowing for zero and full-scale errors

and is expressed in LSBs or as a percentage of full-scale reading.

Single Supply Linearity and Gain Error

The output amplifier on the AD7243 can have true negative off-

sets even when the part is operated from a single +15 V supply.

However, because the negative supply rail (VSS) is 0 V, the out-

put cannot actually go negative. Instead, when the output offset

voltage is negative, the output voltage sits at 0 V, resulting in the

transfer function shown in Figure 1.

OUTPUT

VOLTAGE

0V

{ NEGATIVE

OFFSET

DAC CODE

Figure 1. Effect of Negative Offset (Single Supply)

Pin Mnemonic

1 REFIN

2 REFOUT

3 CLR

4 BIN/COMP

5 SCLK

6 SDIN

7 SYNC

8 DGND

9 LDAC

10 DCEN

11 SDO

12 AGND

13 ROFS

14 VOUT

15 VSS

16 VDD

AD7243 PIN FUNCTION DESCRIPTIONS (DIP and SOIC PIN NUMBERS)

Description

Voltage Reference Input. It is internally buffered before being applied to the DAC. The nominal reference

voltage for specified operation of the AD7243 is 5 V.

Voltage Reference Output. The internal 5 V analog reference is provided at this pin. To operate the part -

using its internal reference, REFOUT should be connected to REFIN.

Clear, Logic Input. Taking this input low sets VOUT to 0 V in both unipolar ranges and the two’s complement

bipolar range and to –REFIN in the offset binary bipolar range.

Logic Input. This input selects the data format to be either binary or two’s complement. In both unipolar

ranges, natural binary format is selected by connecting this input to a Logic “0.” In the bipolar configuration,

offset binary format is selected with a Logic “0” while a Logic “1” selects two’s complement format.

Serial Clock, Logic Input. Data is clocked into the input register on each falling SCLK edge.

Serial Data In, Logic Input. The 16-bit serial data word is applied to this input.

Data Synchronization Pulse, Logic Input. Taking this input low initializes the internal logic in readiness for a

new data word.

Digital Ground. Ground reference for all digital circuitry.

Load DAC, Logic Input. Updates the DAC output. The DAC output is updated on the falling edge of this

signal or alternatively if this line is permanently low, an automatic update mode is selected whereby the DAC

is updated on the 16th falling SCLK pulse.

Daisy-Chain Enable, Logic Input. Connect this pin high if a daisy-chain interface is being used, otherwise

this pin must be connected low.

Serial Data Out, Logic Output. With DCEN at Logic “1” this output is enabled, and the serial data in the

input shift register is clocked out on each falling SCLK edge.

Analog Ground. Ground reference for all analog circuitry.

Output Offset Resistor for the amplifier. It is connected to VOUT for the +5 V range, to AGND for the +10 V

range and to REFIN for the –5 V to +5 V range.

Analog Output Voltage. This is the buffer amplifier output voltage. Three different output voltage ranges can

be chosen: 0 V to +5 V, 0 to +10 V and –5 V to +5 V.

Negative Power Supply (used for the output amplifier only, may be connected to 0 V for single supply

operation or to –12 V to –15 V for dual supplies).

Positive Power Supply (+12 V to +15 V).

–4–

REV. A

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