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参数资料
| 型号： | LTC2488CDE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/30页 |
| 文件大小： | 0K |
| 描述： | IC ADC 16BIT DELTA SIG 14-DFN |
| 标准包装： | 2,500 |
| 位数： | 16 |
| 采样率（每秒）： | 6.9 |
| 数据接口： | MICROWIRE?，串行，SPI? |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 800µW |
| 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： | 14-WFDFN 裸露焊盘 |
| 供应商设备封装： | 14-DFN-EP（4x3） |
| 包装： | 带卷 (TR) |
| 输入数目和类型： | 4 个单端，双极；2 个差分，双极 |
| 配用： | DC1009A-B-ND - BOARD DELTA SIGMA ADC LTC2488 |
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LTC2488
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APPLICATIONS INFORMATION
Whenever SCK is LOW, the LTC2488’s internal pull-up at
SCK is disabled. Normally, SCK is not externally driven if
the device is operating in the internal SCK timing mode.
However, certain applications may require an external
driver on SCK. If the driver goes Hi-Z after outputting a
LOW signal, the internal pull-up is disabled. An external
10k pull-up resistor prevents the device from exiting the
internal SCK mode under this condition.
A similar situation may occur during the sleep state when
CS is pulsed HIGH-LOW-HIGH in order to test the conver-
sion status. If the device is in the sleep state (EOC = 0),
SCK will go LOW. If CS goes HIGH before the time tEOCtest,
the internal pull-up is activated. If SCK is heavily loaded,
the internal pull-up may not restore SCK to a HIGH state
before the next falling edge of CS. The external 10k pull-up
resistor prevents the device from exiting the internal SCK
mode under this condition.
PRESERVING THE CONVERTER ACCURACY
The LTC2488 is designed to reduce as much as possible
sensitivity to device decoupling, PCB layout, anti-aliasing
circuits, line frequency perturbations, and temperature
sensitivity. In order to achieve maximum performance a
few simple precautions should be observed.
Digital Signal Levels
The LTC2488’s digital interface is easy to use. Its digital
inputs SDI, FO, CS, and SCK (in external serial clock mode)
accept standard CMOS logic levels. Internal hysteresis
circuits can tolerate edge transition times as slow as
100μs.
The digital input signal range is 0.5V to VCC – 0.5V. During
transitions, the CMOS input circuits draw dynamic cur-
rent. For optimal performance, application of signals to
the serial data interface should be reserved for the sleep
and data output periods.
During the conversion period, overshoot and undershoot
of fast digital signals applied to both the serial digital in-
terface and the external oscillator pin (FO) may degrade
the converter performance. Undershoot and overshoot
occur due to impedance mismatch of the circuit board
trace at the converter pin when the transition time of an
external control signal is less than twice the propagation
delay from the driver to the input pin. For reference, on a
regular FR-4 board, the propagation delay is approximately
183ps/inch. In order to prevent overshoot, a driver with
a 1ns transition time must be connected to the converter
through a trace shorter than 2.5 inches. This becomes
difcult when shared control lines are used and multiple
reections occur.
Parallel termination near the input pin of the LTC2488 will
eliminate this problem, but will increase the driver power
dissipation. A series resistor from 27Ω to 54Ω (depend-
ing on the trace impedance and connection) placed near
the driver will also eliminate over/under shoot without
additional driver power dissipation.
For many applications, the serial interface pins (SCK, SDI,
CS, FO) remain static during the conversion cycle and
no degradation occurs. On the other hand, if an external
oscillator is used (FO driven externally) it is active during
the conversion cycle. Moreover, the digital lter rejection
is minimal at the clock rate applied to FO. Care must be
taken to ensure external inputs and reference lines do not
cross this signal or run near it. These issues are avoided
when using the internal oscillator.
Driving the Input and Reference
The input and reference pins of the LTC2488 are connected
directly to a switched capacitor network. Depending on
the relationship between the differential input voltage and
the differential reference voltage, these capacitors are
switched between these four pins. Each time a capacitor
is switched between two of these pins, a small amount
of charge is transferred. A simplied equivalent circuit is
shown in Figure 10.
When using the LTC2488’s internal oscillator, the input
capacitor array is switched at 123kHz. The effect of the
charge transfer depends on the circuitry driving the in-
put/reference pins. If the total external RC time constant
is less than 580ns the errors introduced by the sampling
process are negligible since complete settling occurs.
Typically, the reference inputs are driven from a low imped-
ance source. In this case, complete settling occurs even
with large external bypass capacitors. The inputs (CH0 to
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| LTC2488IDE#TRPBF | 功能描述:IC ADC 16BIT DELTA SIG 14-DFN RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:2,500 系列:- 位数:16 采样率（每秒）:15 数据接口:MICROWIRE?，串行，SPI? 转换器数目:1 功率耗散（最大）:480µW 电压电源:单电源 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:38-WFQFN 裸露焊盘 供应商设备封装:38-QFN（5x7） 包装:带卷 (TR) 输入数目和类型:16 个单端，双极；8 个差分，双极 配用:DC1011A-C-ND - BOARD DELTA SIGMA ADC LTC2494 |
| LTC2489CDE#PBF | 功能描述:IC ADC 16BIT DELTA SIG 14-DFN RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:2,500 系列:- 位数:16 采样率（每秒）:15 数据接口:MICROWIRE?，串行，SPI? 转换器数目:1 功率耗散（最大）:480µW 电压电源:单电源 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:38-WFQFN 裸露焊盘 供应商设备封装:38-QFN（5x7） 包装:带卷 (TR) 输入数目和类型:16 个单端，双极；8 个差分，双极 配用:DC1011A-C-ND - BOARD DELTA SIGMA ADC LTC2494 |
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