AD7877 Touch Screen Controller _ BDTIC a Leading Distributor in China

AD7877 Touch Screen Controller

The AD7877 is a 12-bit, successive approximation ADC with a synchronous serial interface and low on resistance switches for driving touch screens. The AD7877 operates from a single 2.7 V to 5.25 V power supply (functional operation to 2.2 V), and features throughput rates of 125 kSPS. The AD7877 features direct battery measurement on two inputs, temperature and touch-pressure measurement.

The AD7877 also has an on-board reference of 2.5 V. When not in use, it can be shut down to conserve power. An external reference can also be applied and varied from 1 V to +VCC, with an analog input range of 0 V to VREF. The device includes a shutdown mode that reduces its current consumption to less than 1 μA.

To reduce the effects of noise from LCDs, the acquisition phase of the on-board ADC is controlled via the STOPACQ pin. User-programmable conversion controls include variable acquisition time and first conversion delay. Up to 16 averages can be taken per conversion. There is also an on-board DAC for LCD back-light or contrast control. The AD7877 runs in either slave or master mode using a conversion sequencer and timer. It is ideal for battery-powered systems such as personal digital assistants with resistive touch screens and other portable equipment.

The part is available in a 32-lead lead frame chip scale package (LFCSP), and a 25-ball wafer level chip scale package (WLCSP). AD7877W model is qualified for automotive applications.

Applications

Personal digital assistants
Smart hand-held devices
Touch screen monitors
Point-of-sale terminals
Medical devices
Cell phones
Pagers

Features and Benefits

4-wire touch screen interface
LCD noise reduction feature (STOPACQ pin)
Automatic conversion sequencer and timer
User-programmable conversion parameters
On-chip temperature sensor:
−40°C to +85°C
On-chip 2.5 V reference

On-chip 8-bit DAC
3 auxiliary analog inputs
1 dedicated and 3 optional GPIOs
3 interrupt outputs
2 direct battery measurement channels (0.5 V to 5 V)
Qualified for automotive applications
See Data Sheet for additional features

Analog to Digital Converters

Capacitive to Digital and Touch Screen Controllers

Data Sheets

Document	note
AD7877: Touch Screen Controller Data Sheet (Rev. E)	PDF 795 kB

Application Notes

Document	note
AN-753: Configuring the AD7877 (Rev. 0)	PDF 247 kB
AN-766: Using the Noise Reduction Feature on the AD7877 (Rev. 0)	PDF 409 kB
AN-738: Using the AD7877 Touch Screen Controller and the Intel PXA250 Processor Under Windows CE.NET (Rev. 0)	PDF 60 kB

Order Information

Part Number	Package	Packing Qty	Temp Range	Price 1000+	RoHS
AD7877ACBZ-REEL7 Last Time Buy	25 Ball WLCSP	REEL 3000	-40 to 85C	2.15	Y
AD7877ACPZ-500RL7 Production	32 ld LFCSP (5x5mm)	OTH 500	-40 to 85C	2.15	Y
AD7877ACPZ-REEL7 Production	32 ld LFCSP (5x5mm)	REEL 1500	-40 to 85C	2.15	Y
AD7877WACPZ-REEL7 Production	32 ld LFCSP (5x5mm)	REEL 1500	-40 to 85C	2.3	Y