Applied Data Systems Bitsy Plus, User Manual, Page: 56 / 68

Bitsy Plus User’s Manual
Page 46 ADS document # 110114-1001A
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 Parameter Min Typ. Max Units
LCD (4.6.2)
V pnl Display power supply (note 7) 3.3 5.0 V
P pnl_pwr Display power (note 8) 2 W
V pnl_data Panel data voltage (note 9) 3.3 3.3 5.0 V
Scan direction (active displays) (4.6.3)
R pnl_rl Pull-up/down resistance 4.7
k
Ω
R pnl_ud Pull-up/down resistance 4.7
k
Ω
V pnl_rl (note 10) 0 V pnl V pnl V
V pnl_ud (note 11) 0 V pnl V pnl V
Contrast Control (passive displays) (3.2.2, 4.6.7)
Vee(-)
Contrast adjust, R
L
=5k
Ω
, JP4: 1-2
-30 -15 V
Vee(+)
Contrast adjust, R
L
=5k
Ω
, JP4: 2-3
15 30 V
Vcon Low-voltage contrast adjust (note 13) 0 Vddx V
Brightness Control (backlight, 4.6.6)
R backlightOn Pull-up (factory option, note 12) 10
k
Ω
Pull-up installed (note 12) 5 V
V backlightOn
No pull-up 30 V
V backlightPWM PWM (note 14) 0 3.3 V
R backlightPWM PWM series resistance (note 14) 1.2 k
Ω
Notes:
7. JP3 selects the display voltage.
8. Total power available depends on system power budget.
9. 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 <= 0.6
Ÿ
Vpnl_pwr (3.0 V) will work reliably with 3.3 V data.
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
the pull-up is not installed, maximum voltage is limited by the transistor ratings.
13. Vcon is the low-voltage PWM signal used to control Vee. It can be used directly with some
passive displays to control contrast.
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 Parameter Min Typ. Max Units
Vdd Supply voltage Vddx V
--- A/D sample resolution 12 bit