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参数资料
| 型号： | LTC1745CFW#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 6/20页 |
| 文件大小： | 0K |
| 描述： | IC ADC 12BIT 25MSPS LN 48TSSOP |
| 标准包装： | 1,800 |
| 位数： | 12 |
| 采样率（每秒）： | 25M |
| 数据接口： | 并联 |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 455mW |
| 电压电源： | 单电源 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 48-TFSOP（0.240"，6.10mm 宽） |
| 供应商设备封装： | 48-TSSOP |
| 包装： | 带卷 (TR) |
| 输入数目和类型： | 2 个单端，双极；1 个差分，双极 |
14
LTC1745
1745f
APPLICATIO S I FOR ATIO
WU
UU
Reference Operation
Figure 5 shows the LTC1745 reference circuitry consisting
of a 2.35V bandgap reference, a difference amplifier and
switching and control circuit. The internal voltage refer-
ence can be configured for two pin selectable input ranges
of 2V(
±1V differential) or 3.2V(±1.6V differential). Tying
the SENSE pin to ground selects the 2V range; tying the
SENSE pin to VDD selects the 3.2V range.
The 2.35V bandgap reference serves two functions: its
output provides a DC bias point for setting the common
mode voltage of any external input circuitry; additionally,
the reference is used with a difference amplifier to gener-
ate the differential reference levels needed by the internal
ADC circuitry.
An external bypass capacitor of 4.7
F or larger is required
for the 2.35V reference output, VCM. This provides a high
frequency low impedance path to ground for internal and
external circuitry. This is also the compensation capacitor
for the reference. It will not be stable without this
capacitor.
The difference amplifier generates the high and low refer-
ence for the ADC. High speed switching circuits are
connected to these outputs and they must be externally
bypassed. Each output has two pins: REFHA and REFHB
for the high reference and REFLA and REFLB for the low
reference. The doubled output pins are needed to reduce
package inductance. Bypass capacitors must be con-
nected as shown in Figure 5.
Other voltage ranges in between the pin selectable ranges
can be programmed with two external resistors as shown
in Figure 6a. An external reference can be used by applying
its output directly or through a resistor divider to SENSE.
It is not recommended to drive the SENSE pin with a logic
device since the logic threshold is close to ground and
VDD. The SENSE pin should be tied high or low as close to
the converter as possible. If the SENSE pin is driven
externally, it should be bypassed to ground as close to the
device as possible with a 1
F ceramic capacitor.
VCM
REFHA
REFLB
SENSE
TIE TO VDD FOR 3.2V RANGE;
TIE TO GND FOR 2V RANGE;
RANGE = 2 VSENSE FOR
1V < VSENSE < 1.6V
2.35V
REFLA
REFHB
4.7
F
4.7
F
INTERNAL ADC
HIGH REFERENCE
BUFFER
0.1
F
1745 F05
LTC1745
4
DIFF AMP
1
F
1
F
0.1
F
INTERNAL ADC
LOW REFERENCE
2.35V BANDGAP
REFERENCE
1.6V
1V
RANGE
DETECT
AND
CONTROL
Figure 5. Equivalent Reference Circuit
VCM
SENSE
2.35V
1.1V
4.7
F
12.5k
1
F
11k
1745 F06a
LTC1745
VCM
SENSE
2.35V
5V
1.25V
6
4
1, 2
4.7
F
1
F
0.1
F
1745 F06b
LTC1745
LT1790-1.25
Figure 6a. 2.2V Range ADC
Figure 6b. 2.5V Range ADC with an External Reference
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| LTC1745IFW | 功能描述:IC ADC SMPL 12BIT 25MSPS 48TSSOP RoHS:否 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1,000 系列:- 位数:12 采样率（每秒）:300k 数据接口:并联 转换器数目:1 功率耗散（最大）:75mW 电压电源:单电源 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:24-SOIC（0.295"，7.50mm 宽） 供应商设备封装:24-SOIC 包装:带卷 (TR) 输入数目和类型:1 个单端，单极；1 个单端，双极 |
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| LTC1745IFW#TR | 功能描述:IC ADC SMPL 12BIT 25MSPS 48TSSOP RoHS:否 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1,000 系列:- 位数:12 采样率（每秒）:300k 数据接口:并联 转换器数目:1 功率耗散（最大）:75mW 电压电源:单电源 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:24-SOIC（0.295"，7.50mm 宽） 供应商设备封装:24-SOIC 包装:带卷 (TR) 输入数目和类型:1 个单端，单极；1 个单端，双极 |
| LTC1745IFW#TRPBF | 功能描述:IC ADC 12BIT 25MSPS LN 48TSSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1,000 系列:- 位数:12 采样率（每秒）:300k 数据接口:并联 转换器数目:1 功率耗散（最大）:75mW 电压电源:单电源 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:24-SOIC（0.295"，7.50mm 宽） 供应商设备封装:24-SOIC 包装:带卷 (TR) 输入数目和类型:1 个单端，单极；1 个单端，双极 |
| LTC1746CFW | 功能描述:IC ADC 14BIT 25MSPS LP 48TSSOP RoHS:否 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1,000 系列:- 位数:12 采样率（每秒）:300k 数据接口:并联 转换器数目:1 功率耗散（最大）:75mW 电压电源:单电源 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:24-SOIC（0.295"，7.50mm 宽） 供应商设备封装:24-SOIC 包装:带卷 (TR) 输入数目和类型:1 个单端，单极；1 个单端，双极 |
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