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| 型号： | EVAL-AD7879EBZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 14/41页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION FOR AD7879 |
| 标准包装： | 1 |
| 主要目的： | 接口，触摸屏控制器 |
| 嵌入式： | 否 |
| 已用 IC / 零件： | AD7879 |
| 主要属性： | 4 线电阻式触控屏控制器，I²C 和 SPI 接口 |
| 次要属性： | 图形用户界面，USB 接口 |
| 已供物品： | 板，线缆，CD，触控屏 |
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AD7879/AD7889
Rev. C | Page 20 of 40
CONVERSION TIMING
Conversion timing or update rate is the rate at which the
AD7879 provides converted values from the ADC so that the
XY positions in the touch screen can be updated. In other
words, the update rate is the timing required to give valid
measurements in the sequencer.
Figure 29 shows conversion timing for a conversion sequence.
F
C
D
TMEASURE
F
C
D
TMEASURE
F
C
D
TMEASURE
F
C
D
F
C
D
TMEASURE TMEASURE TMEASURE
X+
× M
Y+
Z1
Z2
VBAT/AUX
TEMP
07667-
046
Figure 29. Conversion Timing Sequence
FCD is required before each touch screen measurement (X+,
Y+, Z1, and Z2). This time is required to allow the screen inputs
to settle before converting. If the sequence does not contain any
screen channel (VBAT, AUX, or TEMP), only one FCD is added
at start of the sequence. At the end of the sequence, there is
always another FCD.
TMEASURE is the time required to perform one measurement in
the conversion sequence.
TMEASURE = [ACQ (2 μs, 4 μs, 8 μs, 16 μs) + TCONV (7.5 μs) + TSORT
(2 μs)]
where:
ACQ is the acquisition time which is programmable in Control
Register 1. For temperature measurements, ACQ is fixed at 16 μs.
TCONV (typical ADC conversion time) is specified at 7.5 μs.
TSORT is the time needed to sort the new sample within the
median filter array. The TSORT value is approximately 2 μs. If a
median filter is not used (MED =0), the TSORT value is 0.
TMEASURE_MIN = 9.5 μs (ACQ = 2 μs, no median filter)
Conversion time per channel depends on the number of
samples to be converted. The number of samples is pro-
grammed using the following median filter settings:
TCHANNEL = TMEASURE × MED
TCHANNEL_MIN =9.5 μs (ACQ = 2 μs, MED = 0)
TCHANNEL_MAX = 376 μs (ACQ = 16 μs, MED = 16)
Update Rate = [FCD + (TMEASURE × MED)] × N + FCD + TMR
where:
N = number of channels to be measured (1 to 6).
MED = median filter setting (1, 4, 8, 16).
TMR = timer setting (0 μs to 9.4 ms).
The total update rate depends on the median filter settings and
the number of channels in the conversion sequence. The timer
setting (TMR) allows the user more flexibility to program the
update rate.
For example, if
ACQ = 4 us
MED = 8
N = 2
FCD = 1.024 ms
TMR = 620 μs
TMEASURE = 4 + 7.5 + 2 = 13.5 μs
TCHANNEL = (13.5 × 8) = 108 μs
Then
Update rate = [1024 + 108] × 2 + 1024 + 620 = 3.9 ms
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相关代理商/技术参数 |
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| EVAL-AD7887CB | 制造商:Analog Devices 功能描述:EVAL BD FOR 2.7 V TO 5.25 V, MICROPWR, 2CH, 125 KSPS, 12-BIT - Bulk |
| EVAL-AD7887CB4 | 制造商:AD 制造商全称:Analog Devices 功能描述:2.7 V to 5.25 V, Micropower, 2-Channel, 125 kSPS, 12-Bit ADC in 8-Lead MSOP |
| EVAL-AD7887CBZ | 功能描述:BOARD EVAL FOR AD7887 RoHS:是 类别:编程器，开发系统 >> 评估板 - 模数转换器 (ADC) 系列:* 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:- ADC 的数量:1 位数:12 采样率（每秒）:94.4k 数据接口:USB 输入范围:±VREF/2 在以下条件下的电源（标准）:- 工作温度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，软件 |
| EVAL-AD7888CB | 制造商:Analog Devices 功能描述:EVAL KIT FOR 2.7 V TO 5.25 V, MICROPWR, 8CH, 125 KSPS, 12-BI - Bulk |
| EVAL-AD7890-2 | 制造商:Analog Devices 功能描述:AD7890 EVAL BOARD |
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