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參數(shù)資料
| 型號： | ADS7845E |
| 英文描述： | TOUCH SCREEN CONTROLLER |
| 中文描述： | 觸摸屏控制器 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 173K |
| 代理商： | ADS7845E |
6
ADS7845
THEORY OF OPERATION
The ADS7845 is a classic Successive Approximation Reg-
ister (SAR) analog-to-digital (A/D) converter. The architec-
ture is based on capacitive redistribution which inherently
includes a sample/hold function. The converter is fabricated
on a 0.6
μ
s CMOS process.
The basic operation of the ADS7845 is shown in Figure 1.
The device requires an external reference and an external
clock. It operates from a single supply of 2.0V to 5.25V. The
external reference can be any voltage between 1V and +V
CC
.
The value of the reference voltage directly sets the input
range of the converter. The average reference input current
depends on the conversion rate of the ADS7845.
The analog input to the converter is provided via the WIPER
input. In the measurement mode, the lower right corner of the
panel is connected to GND and the upper left corner is
connected to V
CC
. When the lower left corner is connected to
GND and the upper right corner is connected to V
CC
, a “Y”
measurement is made. When the lower left corner is con-
nected to V
CC
and the upper right corner is connected
to GND, a “X” measurement is made. By maintaining a
differential input to the converter and a differential reference
architecture, it is possible to negate the switch’s on-resistance
error (should this be a source of error for the particular
measurement).
ANALOG INPUT
Figure 2 shows a block diagram of the input multiplexer on
the ADS7845, the differential input of the A/D converter, and
the converter’s differential reference. Table I and Table II
show the relationship between the A2, A1, A0, and SER/DFR
control bits and the configuration of the ADS7845. The
control bits are provided serially via the DIN pin—see the
Digital Interface section of this data sheet for more details.
When the converter enters the hold mode, the voltage differ-
ence between the +IN and –IN inputs (see Figure 2) is
captured on the internal capacitor array. The input current on
the analog inputs depends on the conversion rate of the
device. During the sample period, the source must charge the
internal sampling capacitor (typically 25pF). After the ca-
pacitor has been fully charged, there is no further input
current. The rate of charge transfer from the analog source to
the converter is a function of conversion rate.
A2
A1
A0
DRV1
DRV2
AUXIN
INTERRUPT
–IN
(1)
X POSITION
Y POSITION
+REF
(1)
–REF
(1)
0
1
0
1
0
0
1
1
1
1
0
0
ON
GND
GND
GND
GND
OFF
ON
OFF
OFF
ON
OFF
OFF
OFF
+V
REF
+V
REF
+V
REF
+V
REF
GND
GND
GND
GND
ON
ON
DOUT
TABLE I. Input Configuration—Single-Ended Reference Mode (SER/DFR HIGH).
NOTE: (1) Internal node, for clarification only—not directly accessible by the user.
A2
A1
A0
DRV1
DRV2
AUXIN
INTERRUPT
–IN
(1)
X SWITCHES
Y SWITCHES
+REF
(1)
–REF
(1)
0
1
0
1
0
0
1
1
1
1
0
0
ON
LR
LR
GND
GND
OFF
ON
OFF
OFF
ON
OFF
OFF
OFF
UL
UL
LR
LR
GND
GND
ON
ON
+V
REF
+V
REF
DOUT
NOTE: (1) Internal node, for clarification only—not directly accessible by the user.
TABLE II. Input Configuration—Differential Reference Mode (SER/DFR LOW).
FIGURE 1. Basic Operation of the ADS7845.
+V
CC
UL
UR
LL
LR
GND
WIPER
AUXIN
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
DCLK
CS
DIN
BUSY
DOUT
PENIRQ
+V
CC
V
REF
Serial/Conversion Clock
Chip Select
Serial Data In
Converter Status
Serial Data Out
+
1
μ
F
to
10
μ
F
(Optional)
+2.7V to +5V
ADS7845
Auxiliary Input
WIPER
0.1
μ
F
Pen Interrupt
External reference required
with auxiliary input. Otherwise,
NC in differential mode or
V
or external V
in
single-ended mode.
100k
(optional)
0.1
μ
F
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS7845E | 制造商:Texas Instruments 功能描述:5 WIRE TOUCH SCREEN CONTR 16SSOP 制造商:Texas Instruments 功能描述:5 WIRE TOUCH SCREEN CONTR, 16SSOP 制造商:Texas Instruments 功能描述:5 WIRE TOUCH SCREEN CONTR, 16SSOP; Interface Type:5 Wire, Serial, SPI; Resolution (Bits):12bit; Supply Voltage Min:2.7V; Supply Voltage Max:5.5V; Digital IC Case Style:MSOP; No. of Pins:16; Operating Temperature Min:-40C; Operating ;RoHS Compliant: Yes |
| ADS7845E | 制造商:Texas Instruments 功能描述:IC's |
| ADS7845E/2K5 | 功能描述:觸摸屏轉(zhuǎn)換器和控制器 5-wire Touch Screen Controller RoHS:否 制造商:Microchip Technology 類型:Resistive Touch Controllers 輸入類型:3 Key 數(shù)據(jù)速率:140 SPS 分辨率:10 bit 接口類型:4-Wire, 5-Wire, 8-Wire, I2C, SPI 電源電壓:2.5 V to 5.25 V 電源電流:17 mA 工作溫度:- 40 C to + 85 C 封裝 / 箱體:SSOP-20 |
| ADS7845E/2K5G4 | 功能描述:觸摸屏轉(zhuǎn)換器和控制器 5-wire Touch Screen Controller RoHS:否 制造商:Microchip Technology 類型:Resistive Touch Controllers 輸入類型:3 Key 數(shù)據(jù)速率:140 SPS 分辨率:10 bit 接口類型:4-Wire, 5-Wire, 8-Wire, I2C, SPI 電源電壓:2.5 V to 5.25 V 電源電流:17 mA 工作溫度:- 40 C to + 85 C 封裝 / 箱體:SSOP-20 |
| ADS7845EG4 | 功能描述:觸摸屏轉(zhuǎn)換器和控制器 5-wire Touch Screen Controller RoHS:否 制造商:Microchip Technology 類型:Resistive Touch Controllers 輸入類型:3 Key 數(shù)據(jù)速率:140 SPS 分辨率:10 bit 接口類型:4-Wire, 5-Wire, 8-Wire, I2C, SPI 電源電壓:2.5 V to 5.25 V 電源電流:17 mA 工作溫度:- 40 C to + 85 C 封裝 / 箱體:SSOP-20 |
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