Datasheet

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EVM Overview

Figure 1. ADS855xEVM Schematic – Typical Analog Input Section

1.3.2 Analog Supplies – Input Buffers and ADS8556 HV Supplies

The ADS855xEVM Board is configured at the factory for ±12V analog operation. The EVM can tolerate

maximum power supplies of ±15VDC. Care must be taken to ensure the user supplied ±15VDC limit is not

exceeded, or potential damage to the op-amps and the device under test circuits can occur. The user

supplied voltage is filtered and applied to the HVDD and HVSS pins of the ADS8556. The ±HV voltages

are to be applied to J3 pins 1 (HVDD) and 2 (HVSS) referenced to pin 5 (AGND).

1.3.3 Analog +5V Supply

The ADS8556EVM Board requires an independent +5V supply to power the analog portion of the device

under test, the external reference and the external reference buffer. This voltage is applied to J3 pin 3 and

is denoted as AVdd. This supply can be monitored at TP3.

1.3.4 Internal and Reference Voltages

The ADS8556 has an internal programmable 2.5 to 3.0V reference source, which is enabled through the

REFen pin (in hardware mode) or bit C18 in the configuration register (in software mode).

If an external reference is desired, the internal reference must first be disabled. The ADS855xEVM

provides a 2.5V reference source via U11. To use the REF5025 reference, a shunt jumper must be placed

on JP12. Test points 10 and 11 are provided to allow the user to monitor the reference voltage (internal or

external) and may also be used to connect a user provided reference voltage in the range of 0.5 to

3.025V.

SLAU298–November 2009 ADS855xEVM

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