Texas Instruments DAC7741EVM, Руководство пользователя

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9 EVM Operation
9.1 Factory Default Settings
EVM Operation
This section covers in detail the operation of the EVM to provide guidance to the user in evaluating the
onboard DAC, and how to interface the EVM to a specific host processor.
See the DAC7741 data sheet, SBAS248 , for information about its parallel interface and other related
topics.
The EVM board is factory tested and configured to operate in the bipolar output mode.
The EVM board is set to its default configuration from factory as described on the table below to operate
in bipolar
±
10-V mode of operation using the external reference.
Table 2. Factory Default Jumper Settings
Reference Jumper Position Function
W1 OPEN V
REF
output pin is floated and not used for offset adjustment.
W2 OPEN REFEN pin is not used to enable 10-V internal reference.
W3 2-3 External reference source, U3, is routed to REF
IN
to provide 10-V reference.
W4 1-2 Onboard external reference through U3 is connected.
W5 1-2 Negative supply rail of the U2 operational amplifier is supplied with -15 V.
W6 OPEN REFADJ pin is floated.
W7 CLOSE RFB2 pin is strapped to V
OUT
pin for DAC output feedback.
W8 CLOSE TEST pin is tied to DGND.
W9 OPEN SJ pin is floated.
W10 OPEN RFB1 is floated.
W11 CLOSE AGND and DGND are tied together to a common point.
W12 2-3 The LDAC signal used is address decoded, and translated to the DSP_LDAC.
W13 3-4 Buffered output of DAC is fed through W30 and to J4 terminal.
External reference is disconnected from the negative input of U2 to configure U2 for
W14 OPEN
unity gain.
W15 OPEN Configure U2 operational amplifier for unity gain.
W16 OPEN RSTSEL pin is tied high to set DAC reset value to mid-scale.
W17 OPEN RST pin is tied high by default.
W18 1-2 U6 direction control, DIR, set to A-to-B direction.
W19 OPEN RST pin not driven.
W20 CLOSED The U5 output enable pins, OE1 and OE2, are enabled.
W21 OPEN The U6 enable pins, 1G and 2G, are enabled.
W22 OPEN The U6 direction pin, DIR, is not controlled by the R/W signal.
W23 2-3 The U6 is powered with 3.3 VD.
W24 2-3 The DC_CSa# signal is used to control the R/W function.
W25 1-2 The DSP_R/W pin is used to control the CS function.
W26 1-2 The C6x_RD pin is routed for the combination DSP_R/W control signal.
W27 1-2 The C6x_WR pin is routed for the combination DSP_R/W control signal.
W28 OPEN The DSP_CS pin is not used (C5x™ DSP only).
W29 1-2 The DC_CSa# is used to control the enable function of U10.
W30 1-2 V
OUT
is routed to J4 terminal.
W31 OPEN External reference source via pin 20 of J2 or J4 is not used.
DAC7741EVM SLAU093A – October 2002 – Revised May 2005 13