AD7764 datasheet(19/32 Pages) AD

Part #	AD7764

Description	24-Bit, 312 kSPS, 109 dB 誇-? ADC with On-Chip Buffers and Serial Interface

PDF	32 Pages

Scroll/Zoom	100%

Manufacturer	AD [Analog Devices]

Direct Link	http://www.analog.com

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19 / 32 page

AD7764

Rev. 0 | Page 19 of 32

MODULATOR INPUT STRUCTURE

The AD7764 employs a double-sampling front end, as shown in

Figure 37. For simplicity, only the equivalent input circuitry for

VIN+ is shown. The equivalent circuitry for VIN− is the same.

CS2

CPB2

SS4

SH4

CPA

SS2

SH2

CS1

CPB1

SS3

SH3

SS1

SH1

ANALOG

MODULATOR

VIN+

Figure 37. Equivalent Input Circuit

Sampling Switches SS1 and SS3 are driven by ICLK, whereas

Sampling Switches SS2 and SS4 are driven by ICLK. When

ICLK is high, the analog input voltage is connected to CS1. On

the falling edge of ICLK , the SS1 and SS3 switches open and the

analog input is sampled on CS1. Similarly, when ICLK is low,

the analog input voltage is connected to CS2. On the rising edge

of ICLK, the SS2 and SS4 switches open, and the analog input is

sampled on CS2.

Capacitors CPA, CPB1, and CPB2 represent parasitic capacitan-

ces that include the junction capacitances associated with the

MOS switches.

Table 8. Equivalent Component Values

CS1

CS2

CPA

CPB1/2

13 pF

5 pF

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