Display; Touch Panel Controller - Applied Data Systems Bitsy Plus User Manual

Bitsy Plus User's Manual
6.2.2

Display

LCD display panels have a wide range of voltage and data requirements. The Bitsy Plus has a
number of adjustable voltages to support these requirements, as well as controls for brightness
(backlight) and contrast (passive panels only). See section 4.6 for further details.
Symbol
LCD (4.6.2)
V pnl
P pnl_pwr
V pnl_data
Scan direction (active displays) (4.6.3)
R pnl_rl
R pnl_ud
V pnl_rl
V pnl_ud
Contrast Control (passive displays) (3.2.2, 4.6.7)
Vee(-)
Vee(+)
Vcon
Brightness Control (backlight, 4.6.6)
R backlightOn
V backlightOn
V backlightPWM
R backlightPWM
Notes:
7.
8.
9.
10. PNL_RL is pulled up with R87 or pulled down with R22.
11. PNL_UD is pulled up with R79 or pulled down with R17.
12. A pull-up resistor (R116) can be installed on the BacklightOn signal as a factory option. If
13. Vcon is the low-voltage PWM signal used to control Vee. It can be used directly with some
14. The backlight on/off and PWM outputs are driven by the ADSmartIO controller
6.2.3

Touch Panel Controller

The Bitsy Plus uses touch panel controllers from Burr Brown. It uses the ADS7846 to support
four-wire analog-resistive touch panels and the ADS7845 to support five-wire panels. The system
is factory-configured for use with four-wire panels. All touch-panel signals are ESD and RF
protected. The touch panel controller is powered during sleep mode and can generate an interrupt
to wake the system.
Symbol
Vdd
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Parameter
Display power supply (note 7)
Display power (note 8)
Panel data voltage (note 9)
Pull-up/down resistance
Pull-up/down resistance
(note 10)
(note 11)
Contrast adjust, R
Contrast adjust, R
Low-voltage contrast adjust (note 13)
Pull-up (factory option, note 12)
Pull-up installed (note 12)
No pull-up
PWM (note 14)
PWM series resistance (note 14)
JP3 selects the display voltage.
Total power available depends on system power budget.
Systems are configured at the factory with buffers for 3.3 or 5 V panel data. R289 selects
5 V power for the buffers while R288 selects 3.3 V power (they're located under the
opening for the PCMCIA header about 1cm from the right, ejector corner of the board). 5 V
displays with Vih <= 0.6ŸVpnl_pwr (3.0 V) will work reliably with 3.3 V data.
the pull-up is not installed, maximum voltage is limited by the transistor ratings.
passive displays to control contrast.
Parameter
Supply voltage
A/D sample resolution
Min
3.3
3.3
0
0
-30
=5kΩ, JP4: 1-2
L
=5kΩ, JP4: 2-3 15
L
0
0
Min
Typ. Max Units
5.0 V
2 W
3.3 5.0 V
4.7
kΩ
4.7
kΩ
V pnl V pnl V
V pnl V pnl V
-15 V
30 V
Vddx V
10
kΩ
5 V
30 V
3.3 V
1.2
kΩ
Typ. Max Units
Vddx V
12 bit
ADS document # 110114-1001A