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 +V_CC, with an analog input range of 0 V to V_REF. 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).

Applications

Personal digital assistants

Smart hand-held devices

Touch screen monitors

Point-of-sale terminals

Medical devices

Cell phones

Pagers

Part#	Res	Throughput Rate	# of Inputs	Operating Pwr Diss
AD7450	12	1MSPS	1	1.3mW
AD7466	12	200KSPS	1	900µW
AD7294	12	200KSPS	9	-
AD7467	10	200KSPS	1	630µW
AD7888	12	125KSPS	8	3.5mW
AD7927	12	200KSPS	8	7.5mW
AD7928	12	1MSPS	8	13.5mW
AD7938	12	1.5MSPS	8	16mW
AD7859B	12	200KSPS	8	30mW
AD7858B	12	200KSPS	8	33mW
AD7891	12	500KSPS	8	100mW

The model number is a specific version of a generic that can be purchased or sampled.

Status indicates the current lifecycle of the product. This can be one of 4 stages:

• Pre-Release: The model has not been released to general production, but samples may be available.
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• Obsolete: The specific part is obsolete and no longer available. Other models listed in the table may still be available (if they have a status that is not obsolete).

The package for this IC (i.e. DIP, SOIC, BGA). An Evaluation Board is a board engineered to show the performance of the model, the part is included on the board.

For detailed drawings and chemical composition please consult our  Package Site

Pin Count is the number of pins, balls, or pads on the device. Pin-out diagrams & pin function descriptions may be found in the datasheet.

This is the acceptable operating range of the device. The various ranges specified are as follows:

• Commercial: 0 to +70 degrees Celsius
• Military : -55 to +125 degrees Celsius
• Industrial: Temperature ranges may vary by model. Please consult the datasheet for more information.
• Automotive: -40 to +125 degrees Celsius

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