Datasheet

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4.1 TSC Power
4.2 Stand-Alone Operation
4.3 USB-MODEVM Interface Power
4.4 Reference Voltage
Power Supplies
Power for the ADS7845 VCC can be supplied either from +5V or from +3.3V. JMP4 selects which of these
voltages is routed to the ADS7845. When JMP4 is in the default factory condition (shunt on pins 5-6),
power to the TSC comes from J3.3 (+5VA). When the shunt is installed on JMP4 pins 3-4, power comes
from J3.9 (+3.3VD). A third supply option is to place a shunt on JMP4 pins 1-2, and supply a voltage from
J3.8 (VD1), which must be within the specified operating range of the ADS7845.
When used as a stand-alone EVM, the analog power can be applied to TP1, referenced to TP2.
CAUTION
Verify that all power supplies are within the safe operating limits shown on
the ADS7845 data sheet before applying power to the EVM.
The USB-MODEVM Interface Board can be powered from several different sources:
• USB
• 6VDC-10VDC AC/DC wall supply (not included)
• Laboratory power supply
When powered from the USB connection, JMP6 should have a shunt from pins 1-2 (this is the default
factory configuration). When powered from 6V-10VDC, either through the J8 terminal block or J9 barrel
jack, JMP6 should have a shunt installed on pins 2-3. If power is applied in any of these ways, onboard
regulators generate the required supply voltages and no further power supplies are necessary.
If laboratory supplies are used to provide the individual voltages required by the USB-MODEVM Interface
Board, JMP6 should have no shunt installed. Voltages are then applied to J2 (+5VA), J3 (+5VD), J4
(+1.8VD), and J5 (+3.3VD). The +1.8VD and +3.3VD can also be generated on the board by the onboard
regulators from the +5VD supply; to enable this option, the SW1 switches need to be set in the ON
position (lower position, looking at the board with text reading right-side up) to enable the regulators. If
+1.8VD and +3.3VD are supplied externally, disable the onboard regulators by placing the SW1 switches
in the OFF position.
Each power-supply voltage has an LED (D1-D7) that lights when the power supplies are active.
The ADS7845 requires a voltage reference. An external reference may be supplied through J1 pin 20 on
the ADS7845EVM, referenced to analog ground (J1 pin 18 on the ADS7845EVM). JMP1 must be installed
across positions 5-6 in order to route this external reference voltage to the ADS7845.
CAUTION
Verify that the external reference voltage is within the safe operating limits
shown on the ADS7845 data sheet before applying power to the EVM.
A 2.5V reference is supplied on the ADS7845EVM, and can be selected for use by connecting JMP1 pins
3-4. Alternatively, the supply voltage can be used as the voltage reference by connecting pins 1-2 on
JMP1.
ADS7845EVM and ADS7845EVM-PDK4 SBAU122 – March 2006
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