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PDF A8946 Data sheet ( Hoja de datos )
| Número de pieza | A8946 | |
| Descripción | TOUCH SCREEN DRIVER | |
| Fabricantes | AiT Semiconductor | |
| Logotipo |  |
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AiT Semiconductor Inc.
www.ait-ic.com
A8946
TOUCH SCREEN DRIVER
4-WIRE RESISTANCE, LOW-VOLTAGE I/O INTERFACE
DESCRIPTION
FEATURES
The A8946 is a 4-wire touch screen driver which
supports a low-voltage I/O interface from 1.5V to
5.25V.
1.5V to 5.25V digital I/O
2.2V to 5.25V operation
The A8946 has an on-chip 2.5V reference that can
4-wire I/F
be used for the auxiliary input, battery monitor, and
Internal 2.5V reference
temperature measurement modes. The reference
can also be powered down when not used to
Direct battery measurement(0V to 6V)
conserve power. The internal reference operates
Programmable 8 or 12 bit Resolution
down to 2.7V supply voltage, while monitoring the
battery voltage from 0V to 6V.
Temperature measurement
The A8946 is a highly integrated driver for portable
applications with 4-wire resistive touch panel such
Touch-pressure measurement
Available in QFN16 & TSSOP16 Package.
as, PDA, portable instruments, cellular phone, etc.
The A8946 is available in QFN16 & TSSOP16
APPLICATION
package.
Cellular Phones
ORDERING INFORMATION
Personal Digital Assistants
Package Type
Part Number
QFN16
Q16
A8946Q16R
A8946Q16VR
TSSOP16
TMX16
A8946TMX16R
A8946TMX16VR
Note
R：Tape & Reel
V: Green Package
AiT provides all Pb free products
Suffix “V” means Green Package
Portable Instruments
Touch Screen Monitors
Screen Signature Board
Digital Still Camera
Typical Application
REV1.2 - DEC 2007 RELEASED – OCT 2008 REVISED -
-1-
1 page  
AiT Semiconductor Inc.
www.ait-ic.com
A8946
TOUCH SCREEN DRIVER
4-WIRE RESISTANCE, LOW-VOLTAGE I/O INTERFACE
Symbol
Parameter
Conditions
Min Typ
Max
Range
1.0 +VCC
Reference Input Input Impedance
SER/ = D, PD1=0,
Internal Reference Off
1
Internal Reference On
250
Logic Family
CMOS
Digital
Input / Output
VIH
VIL
VOH
VOL
Data Format
+VCCNOTE5
I | IH | ≦+5uA
I | IL | ≦+5uA
LOH = -250 uA
LOL = 250uA
Specified Performance
IOVDD*0.7
-0.3
IOVDD*0.8
2.7
Straight
Binary
IOVDD+0.3
0.3*IOVDD
0.4
3.6
Operating Range
2.2
5.25
Power-Supply
Requirements
IOVDONOTE6
1.5 +VCC
Internal Reference Off
280 650
Internal Reference On
780
Quiescent CurrentNOTE7 FSAMPLE= 12.5 KHz
220
Power-Down Mode with
CS =DCLK=DIN=IOVDD
3
Power Dissipation
+VCC=+2.7V
1.8
Temperature
Range
Specified Performance
-40 +85
Qn-Resistance
Y+，X+
5
Switch Drivers
Y-，X-
6
Drive CurrentNOTE2
Duration 100ms
50
NOTE1. LSB means least significant bit. With VREF =F+2.5V, one LSB is 610μV.
NOTE2. Assured by design, but not tested. Exceeding 50mA source current may result in device degradation.
NOTE3. Difference between TEMP0 and TEMP1 measurement, no calibration necessary.
NOTE4. Temperature drift is –2.1mV/°C.
NOTE5. A8946 operates down to 2.2V.
NOTE6. IOVDD must be - +VCC.
NOTE7. Combined supply current from +VCC and IOVDD. Typical values obtained from conversions on AUX input with PD0 = 0.
Unit
V
GΩ
Ω
V
V
V
V
V
V
V
uA
uA
uA
uA
mW
°C
Ω
Ω
mA
REV1.2 - DEC 2007 RELEASED – OCT 2008 REVISED -
-5-
5 Page 
AiT Semiconductor Inc.
www.ait-ic.com
A8946
TOUCH SCREEN DRIVER
4-WIRE RESISTANCE, LOW-VOLTAGE I/O INTERFACE
The second mode does not require a test temperature calibration, but uses a two-measurement method to
eliminate the need for absolute temperature calibration and for achieving 2°C accuracy. This mode requires a
second conversion with an address of A2 = 1, A1 = 1, and A0 = 1, with a 91 times larger current. The voltage
difference between the first and second conversion using 91 times the bias current is represented by
KT/q * ln (N), where N is the current ratio = 91, K = Boltzmann’s constant (1.38054 * 10–23 electron volts/
degrees Kelvin), q = the electron charge (1.602189 * 10–19 C), and T = the temperature in degrees Kelvin. This
method can provide improved absolute temperature measurement over the first mode at the cost of less
resolution (1.6°C/LSB). The equation for solving for °K is:
°K = q * △V/(k • ln (N))
Where, V = V (I91) – V (I1) (in mV)
∴ °K = 2.573 °K/mV * △V
°C = 2.573 * △V(mV) – 273°K
NOTE: The bias current for each diode temperature measurement is only on for 3 clock cycles (during the acquisition mode) and,
therefore, does not add any noticeable increase in power, especially if the temperature measurement only occurs occasionally.
Battery Measurement
An added feature of the A8946 is the ability to monitor the battery voltage on the other side of the voltage
regulator (DC/DC converter), as shown in Fig 5. The battery voltage can vary from 0V to 6V, while maintaining
the voltage to the A8946 at 2.7V, 3.3V, etc. The input voltage (VBAT) is divided down by 4 so that a 5.5V
battery voltage is represented as 1.375V to the ADC. This simplifies the multiplexer and control logic. In order
to minimize the power consumption, the divider is only on during the sampling period when A2 = 0, A1 = 1,
and A0 = 0 (see Table 1. for the relationship between the control bits and configuration of the A8946).
REV1.2 - DEC 2007 RELEASED – OCT 2008 REVISED -
- 11 -
11 Page | ||
| Páginas | Total 25 Páginas | |
| PDF Descargar | [ Datasheet A8946.PDF ] | |
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