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參數(shù)資料
| 型號： | ADS807E |
| 英文描述： | 12-Bit, 53MHz Sampling ANALOG-TO-DIGITAL CONVERTER |
| 中文描述： | 12位，53MHz采樣模擬數(shù)字轉(zhuǎn)換器 |
| 文件頁數(shù)： | 13/15頁 |
| 文件大?。?/td> | 225K |
| 代理商： | ADS807E |
13
ADS807
REFERENCE OPERATION
The internal reference consists of a bandgap voltage refer-
ence, the drivers for the top and bottom reference, and the
resistive reference ladder. The bandgap reference circuit
includes logic functions that allow setting the analog input
swing of the ADS807 to a differential full-scale range of
either 2Vp-p or 3Vp-p by simply tying the FS
SEL
pin to a
LOW or HIGH potential, respectively. While operating the
ADS807 in the external reference mode, the buffer amplifi-
ers for the REFT and REFB are disabled. The ADS807 has
an internal 50k
pull-down resistor at the range select pin
(RSEL). Therefore, this pin can be either hardwired to
ground or left unconnected, which will default the converter
to a 2Vp-p full-scale input range (FSR). While set for the
2Vp-p range, the top and bottom reference voltages will
be REFT = +3.0V and REFB = +2.0V. Switching to the
3Vp-p range changes those voltages to REFT = +3.25V and
REFB = +1.75V. The reference buffers can be utilized to
supply up to 1mA (sink and source) to external circuitry. To
ensure proper operation with any reference configuration, it
is necessary to provide solid bypassing at all reference pins
in order to keep the clock feedthrough to a minimum, see
Figure 6. Good performance requires using 0.1
μ
F low in-
ductance capacitors. All bypassing capacitors should be
located as close to their respective pins as possible.
USING EXTERNAL REFERENCES
For even more design flexibility, the internal reference can
be disabled and an external reference voltage used. The
utilization of an external reference may be considered for
applications requiring higher accuracy, improved tempera-
ture performance, or a wide adjustment range of the
converter’s full-scale range. In multichannel applications,
the use of a common external reference has the benefit of
obtaining better matching and drift of the full-scale range
between converters. Figure 7 gives an example of an exter-
nal reference circuit using a single-supply, low power, dual
op amp (OPA2234).
The external references can vary as long as the value of the
external top reference (REFT EXT) stays within the range of
V
S
– 1.70V and REFB + 0.4V, and the external bottom
reference (REFB EXT) stays within 1.70V and REFT – 0.4V.
Note that the function of the range selector pin (FS
SEL
) is
disabled while the converter operates in external reference
mode. Setting the ADS807 for external reference mode re-
quires the INT/EXT pin (pin 18) to be HIGH.
The logic level applied to the INT/EXT pin of the ADS807
determines if the converter operates with either the built-in
reference or external reference voltages. Because this function
pin has an internal 50k
pull-up resistor, the default configu-
ration is external reference mode. Grounding this pin will
activate the internal reference option.
The input track and hold amplifier is differential. A posi-
tive 1Vp-p on the IN and its compliment, a negative
1Vp-p, on the IN (as shown in Figure 3) results in 2Vp-p
on the output of the T/H. Likewise, 2Vp-p on the IN and
0Vp-p on the IN (as shown in Figure 4) results in 2Vp-p
on the output of the T/H. Therefore, the reference volt-
ages, REFT and REFB, are the same for both differential
and single-ended inputs. See Table I.
The external references may be changed for different tasks.
The ADS807 will follow the external references with a
latency of 8 to 10 clock cycles. If it is desired to use INT/EXT
and FS
SEL
to change the configuration of a circuit for different
tasks, a large amount of time must be allowed. This time could
be hundreds of microseconds. Refer to the Diagram on the
front page. Note that there is no disconnect for external
references. If it is desired to switch between internal and
external references, disconnect switches must be added be-
tween the external references and the ADS807.
FIGURE 7. Example for an External Reference Driver Using the Dual, Single-Supply Op Amp, OPA2234.
REFT
CM
0.1
μ
F
(1)
(1)
(1)
REFB
ADS807
0.1
μ
F
0.1
μ
F
10
μ
F
NOTE: (1) Optional.
+
10
μ
F
+
10
μ
F
+
FIGURE 6. Recommended Bypassing for the Reference Pins.
OPA2234
A1
OPA2234
A2
R
3
R
4
R
2
R
1
+5V
+5V
0.1μF
10μF
> 1.70V
< 3.30V
Top Reference
Bottom Reference
+
4.7k
REF1004
+2.5V
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS807E/1K | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 53 MSPS SE/Diff imputs RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS807E/1KG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 53 MSPS SE/Diff imputs RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS807EG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 53 MSPS SE/Diff imputs RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS808 | 制造商:BB 制造商全稱:BB 功能描述:12-Bit, 70MHz Sampling ANALOG-TO-DIGITAL CONVERTER |
| ADS808Y/250 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 70MHz Sampling ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
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