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參數資料
| 型號： | AD7892SQ |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators |
| 中文描述： | 雙通道高效率，低噪聲，同步降壓型開關穩壓器 |
| 文件頁數： | 9/14頁 |
| 文件大?。?/td> | 144K |
| 代理商： | AD7892SQ |
AD7892
REV. C
–9–
CIRCUIT DESCRIPTION
The AD7892 is a fast, 12-bit single supply A/D converter. It
provides the user with signal scaling, track/hold, reference, A/D
converter and versatile interface logic functions on a single chip.
The signal scaling on the AD7892-1 allows the part to handle
either
±
5 V or
±
10 V input signals while operating from a single
+5 V supply. The AD7892-2 handles a 0 V to +2.5 V analog
input range, while signal scaling on the AD7892-3 allows it to
handle
±
2.5 V input signals when operating from a single supply.
The part requires a +2.5 V reference which can be provided from
the part’s own internal reference or from an external reference
source.
Conversion is initiated on the AD7892 by pulsing the
CONVST
input. On the rising edge of
CONVST
, the track/hold goes
from track mode to hold mode and the conversion sequence is
started. At the end of conversion (falling edge of
EOC
), the
track/hold returns to tracking mode and the acquisition time
begins. Conversion time for the part is 1.47
μ
s (AD7892-3) and
the track/hold acquisition time is 200 ns (AD7892-3). This allows
the AD7892-3 to operate at throughput rates up to 600 kSPS.
The AD7892-1 and AD7892-2 are specified with a 1.6
μ
s con-
version and 400 ns acquisition time allowing a throughput rate
of 500 kSPS.
Track/Hold Section
The track/hold amplifier on the AD7892 allows the ADC to
accurately convert an input sine wave of full-scale amplitude to
12-bit accuracy. The input bandwidth of the track/hold is greater
than the Nyquist rate of the ADC even when the ADC is oper-
ated at its maximum throughput rate of 600 kHz (i.e., the track/
hold can handle input frequencies in excess of 300 kHz).
The track/hold amplifier acquires an input signal to 12-bit accu-
racy in less than 200 ns. The operation of the track/hold is
essentially transparent to the user. The track/hold amplifier
goes from its tracking mode to its hold mode on the rising edge
of
CONVST
. The aperture time for the track/hold (i.e., the
delay time between the external
CONVST
signal and the track/
hold actually going into hold) is typically 15 ns. At the end of
conversion, the part returns to its tracking mode. The acquisi-
tion time of the track/hold amplifier begins at this point.
Reference Section
The AD7892 contains a single reference pin, labelled REF OUT/
REF IN, which either provides access to the part’s own +2.5 V
reference or to which an external +2.5 V reference can be con-
nected to provide the reference source for the part. The part is
specified with a +2.5 V reference voltage. Errors in the refer-
ence source will result in gain errors in the AD7892’s transfer
function and will add to the specified full-scale errors on the
part. On the AD7892-1 and AD7892-3, it will also result in an
offset error injected in the attenuator stage.
The AD7892 contains an on-chip +2.5 V reference. To use this
reference as the reference source for the AD7892, simply con-
nect a 0.1
μ
F disc ceramic capacitor from the REF OUT/
REF IN pin to AGND. The voltage that appears at this pin is
internally buffered before being applied to the ADC. If this
reference is required for use external to the AD7892, it should
be buffered as the part has a FET switch in series with the refer-
ence output resulting in a source impedance for this output of
5.5 k
nominal. The tolerance on the internal reference is
±
10 mV at 25
°
C with a typical temperature coefficient of
25 ppm/
°
C and a maximum error over temperature of
±
25 mV.
If the application requires a reference with a tighter tolerance or
the AD7892 needs to be used with a system reference, then the
user has the option of connecting an external reference to this
REF OUT/REF IN pin. The external reference will effectively
overdrive the internal reference and thus provide the reference
source for the ADC. The reference input is buffered before
being applied to the ADC with the maximum input current is
±
100
μ
A. Suitable reference sources for the AD7892 include the
AD680, AD780 and REF43 precision +2.5 V references.
INTERFACING
The part provides two interface options, a 12-bit parallel inter-
face and a three-wire serial interface. The required interface
mode is selected via the MODE pin. The two interface modes
are discussed in the following sections.
Parallel Interface Mode
The parallel interface mode is selected by tying the MODE
input to a logic high. Figure 2 shows a timing diagram illustrat-
ing the operational sequence of the AD7892. The on-chip
track/hold goes into hold mode, and conversion is initiated on
the rising edge of the
CONVST
signal. When conversion is
complete, the end of conversion line (
EOC
) pulses low to indi-
cate that new data is available in the AD7892’s output register.
This
EOC
line can be used to drive an edge-triggered interrupt
of a microprocessor. The falling edge of the
RD
signal should
occur 200 ns prior to the next rising edge of
CONVST
.
CS
and
RD
going low accesses the 12-bit conversion result. In systems
where the part is interfaced to a gate array or ASIC, this
EOC
VALID
DATA
t
CONV
t
8
t
5
t
4
t
7
t
6
t
2
t
1
THREE-STATE
CONVST
(I)
EOC
(O)
CS
(I)
RD
(I)
DB0–DB11 (O)
NOTE:
I = INPUT; O = OUTPUT
t
ACQ
t
3
t
9
THREE-STATE
Figure 2. Parallel Mode Timing Diagram
相關PDF資料 |
PDF描述 |
|---|---|
| AD7892AN-1 | LC2MOS Single Supply, 12-Bit 600 kSPS ADC |
| AD7892AN-2 | LC2MOS Single Supply, 12-Bit 600 kSPS ADC |
| AD7892AN-3 | LC2MOS Single Supply, 12-Bit 600 kSPS ADC |
| AD7892AR-1 | LC2MOS Single Supply, 12-Bit 600 kSPS ADC |
| AD7892BN-1 | LC2MOS Single Supply, 12-Bit 600 kSPS ADC |
相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7892SQ-1 | 功能描述:模數轉換器 - ADC Bipolar Input Parallel 12B 600kSPS RoHS:否 制造商:Analog Devices 通道數量: 結構: 轉換速率: 分辨率: 輸入類型: 信噪比: 接口類型: 工作電源電壓: 最大工作溫度: 安裝風格: 封裝 / 箱體: |
| AD7893ACHIPS-10 | 功能描述:12 Bit Analog to Digital Converter 1 Input 1 SAR Die 制造商:analog devices inc. 系列:- 包裝:托盤 - 晶粒 零件狀態:上次購買時間 位數:12 采樣率（每秒）:117k 輸入數:1 輸入類型:單端 數據接口:SPI 配置:S/H-ADC 無線電 - S/H:ADC:1:1 A/D 轉換器數:1 架構:SAR 參考類型:外部 電壓 - 電源，模擬:5V 電壓 - 電源，數字:5V 特性:- 工作溫度:-40°C ~ 85°C 封裝/外殼:模具 供應商器件封裝:模具 標準包裝:1 |
| AD7893ACHIPS-2 | 功能描述:12 Bit Analog to Digital Converter 1 Input 1 SAR Die 制造商:analog devices inc. 系列:- 包裝:管件 零件狀態:上次購買時間 位數:12 采樣率（每秒）:117k 輸入數:1 輸入類型:單端 數據接口:SPI 配置:S/H-ADC 無線電 - S/H:ADC:1:1 A/D 轉換器數:1 架構:SAR 參考類型:外部 電壓 - 電源，模擬:5V 電壓 - 電源，數字:5V 特性:- 工作溫度:-40°C ~ 85°C 封裝/外殼:模具 供應商器件封裝:模具 標準包裝:1 |
| AD7893ACHIPS-5 | 功能描述:12 Bit Analog to Digital Converter 1 Input 1 SAR Die 制造商:analog devices inc. 系列:- 包裝:托盤 - 晶粒 零件狀態:上次購買時間 位數:12 采樣率（每秒）:117k 輸入數:1 輸入類型:單端 數據接口:SPI 配置:S/H-ADC 無線電 - S/H:ADC:1:1 A/D 轉換器數:1 架構:SAR 參考類型:外部 電壓 - 電源，模擬:5V 電壓 - 電源，數字:5V 特性:- 工作溫度:-40°C ~ 85°C 封裝/外殼:模具 供應商器件封裝:模具 標準包裝:1 |
| AD7893AN-10 | 功能描述:IC ADC 12BIT SRL T/H LP 8-DIP RoHS:否 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:- 標準包裝:1 系列:- 位數:14 采樣率（每秒）:83k 數據接口:串行，并聯 轉換器數目:1 功率耗散（最大）:95mW 電壓電源:雙 ± 工作溫度:0°C ~ 70°C 安裝類型:通孔 封裝/外殼:28-DIP（0.600"，15.24mm） 供應商設備封裝:28-PDIP 包裝:管件 輸入數目和類型:1 個單端，雙極 |
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