AD7829BN datasheet(10/20 Pages) AD

tên linh kiện	AD7829BN

Giải thích chi tiết về linh kiện	3 V/5 V, 2 MSPS, 8-Bit, 1-, 4-, 8-Channel Sampling ADCs

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AD7822/AD7825/AD7829

–10–

REV. B

CONVST

DB0–DB7

A0–A2

EOC

CS

RD

t2

t1

t3

t13

VALID

DATA

ADDRESS CHANNEL y

TRACK CHx

HOLD CHx

TRACK CHy

HOLD CHy

120ns

Figure 12. Channel Hopping Timing

There is a minimum time delay between the falling edge of RD

and the next falling edge of the CONVST signal, t13. This is the

minimum acquisition time required of the track-and-hold in

order to maintain 8-bit performance. Figure 13 shows the typical

performance of the AD7825 when channel hopping for various

acquisition times. These results were obtained using an external

reference and internal VMID while channel hopping between

VIN1 and VIN4 with 0 V on Channel 4 and 0.5 V on Channel 1.

ACQUISITION TIME – ns

8.0

5.0

500

10

200

100

50

40

30

20

15

7.5

7.0

6.5

6.0

5.5

8.5

Figure 13. Effective Number of Bits vs. Acquisition Time

for the AD7825

The on-chip track-and-hold can accommodate input frequen-

cies to 10 MHz, making the AD7822, AD7825, and AD7829

ideal for subsampling applications. When the AD7825 is con-

verting a 10 MHz input signal at a sampling rate of 2 MSPS,

the effective number of bits typically remains above seven,

corresponding to a signal-to-noise ratio of 42 dBs as shown

in Figure 14.

INPUT FREQUENCY – MHz

50

38

0.2

10

1

3

4

568

48

46

44

42

40

fSAMPLE = 2MHz

Figure 14. SNR vs. Input Frequency on the AD7825

POWER-UP TIMES

The AD7822/AD7825/AD7829 have a 1

µs power-up time when

using an external reference and a 25

µs power-up time when using

the on-chip reference. When VDD is first connected, the AD7822,

AD7825, and AD7829 are in a low current mode of operation.

Ensure that the CONVST line is not floating when VDD is applied,

as if there is a glitch on CONVST while VDD is rising, the part will

attempt to power up before VDD has fully settled and could enter

an unknown state. In order to carry out a conversion, the AD7822,

AD7825, and AD7829 must first be powered up. The AD7829 is

powered up by a rising edge on the CONVST pin and a conversion

is initiated on the falling edge of CONVST. Figure 15 shows how

to power up the AD7829 when VDD is first connected or after the

AD7829 has been powered down using the CONVST pin when

using either the on-chip, or an external, reference. When using

an external reference, the falling edge of CONVST may occur

before the required power-up time has elapsed; however, the

conversion will not be initiated on the falling edge of CONVST but

rather at the moment when the part has completely powered up,

i.e., after 1

µs. If the falling edge of CONVST occurs after the required

power-up time has elapsed, then it is upon this falling edge that a

conversion is initiated. When using the on-chip reference, it is nec-

essary to wait the required power-up time of approximately 25

µs

before initiating a conversion; i.e., a falling edge on CONVST

may not occur before the required power-up time has elapsed,

when VDD is first connected or after the AD7829 has been powered

down using the CONVST pin as shown in Figure 15.

VDD

tPOWER-UP

1 s

CONVST

VDD

CONVST

tPOWER-UP

25 s

CONVERSION

INITIATED HERE

CONVERSION

INITIATED HERE

EXTERNAL REFERENCE

ON-CHIP REFERENCE

Figure 15. AD7829 Power-Up Time

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nhà sản xuất	tên linh kiện	bảng dữ liệu	Giải thích chi tiết về linh kiện
Analog Devices	AD7829BN	525Kb / 28P	3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs REV. C
Analog Devices	AD7829BNZ1	525Kb / 28P	3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs REV. C

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nhà sản xuất	tên linh kiện	bảng dữ liệu	Giải thích chi tiết về linh kiện
Analog Devices	AD7825	525Kb / 28P	3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs REV. C
	AD7829	525Kb / 28P	3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs REV. C
	AD7822	525Kb / 28P	3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs REV. C
	AD7822	525Kb / 28P	3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs REV. C
	AD7829-1	390Kb / 20P	3 V/5 V, 2 MSPS, 8-Bit, 8-Channel ADC REV. 0
	AD7829-1	390Kb / 20P	3 V/5 V, 2 MSPS, 8-Bit, 8-Channel ADC REV. 0
	AD7829-1	361Kb / 21P	3 V/5 V, 2 MSPS, 8-Bit, 8-Channel ADC
	AD7827	189Kb / 12P	3 V/5 V, 1 MSPS, 8-Bit, Serial Interface Sampling ADC REV. 0
	AD7827	185Kb / 12P	3 V/5 V, 1 MSPS, 8-Bit, Serial Interface Sampling ADC REV. 0
	AD7859	405Kb / 28P	3 V to 5 V Single Supply, 200 kSPS 8-Channel, 12-Bit Sampling ADCs REV. A

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