Linear Technology DC1427A Quick Start Manual page 3

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC1427A
CONNECTIONS TO THE DC1427A
Figure 1 shows the connections to the DC1427A.
Refer to the Controlled demo circuit's Quick Start
Guide for additional required connections.
Isolated Supply Options Isolated Supply O Isolated Supply O Isolated Supply O ptions ptions ptions
An LT3439 low-noise switching power supply pro-
vides isolated power to the demonstration circuit
under evaluation and to the isolation circuitry. This
is adequate in many cases, however an external
power supply can be used to reduce the load on
the host computer's USB port or to reduce power
supply noise in the circuit under test.
The LT3439 switching power supply is enabled by
default but may be disabled by moving jumper
JP5 (ISO, to the left) to the OFF position. This al-
lows the isolated side of the board and the dem-
onstration circuit under evaluation to be powered
separately. This is recommended when testing
precision components such as high resolution
ADCs and DACs. After moving JP5 ISO to the
OFF position, apply a clean, regulated power sup-
ply from 7v to 10V to the V+ and AGND turret
posts.
Isolated Digital Supply Isolated Digital Supply Isolated Digital Supply Isolated Digital Supply
The signal levels on the digital interface are de-
termined by the VCCA voltage. The onboard regu-
lator can be set to 5V, 3.3V, 2.7V by installing JP6
in the appropriate position (remove jumper for
2.7V.) Selecting EXT shuts the regulator down,
and an external supply between 2.7 and 5V must
be applied to the VCCA turret post.
I2C/SMBUS/PMBUS CONTROLLER
The +5V turret is the digital supply for the isolated
portion of DC1427A. Do not draw current from this
point
LED Indicators LED Indicators LED Indicators LED Indicators
Two LED indicators are provided. The "ISO PWR"
LED is lit when either the onboard switching
power supply is running or external power is ap-
plied to the isolated side of the board.
The "COMMAND" LED indicates that a command
has been sent to the board by the host PC and is
waiting to be executed. The LED may not appear
to be blinking in some cases, as the duty cycle
may be very short.
J J J J umper umper S S S S ummary umper umper ummary ummary ummary
Some jumpers on the DC1427 board are for future
use and MUST be left in the default positions.
JP1 – PROG – Microcontroller in-circuit program-
ming header, do NOT install jumper, make no
connections.
JP2 – MODE – do NOT install jumper, make no
connections.
JP3 – Watchdog enable - do NOT install jumper,
make no connections.
JP4 – EE – Jumper MUST be in the EN position.
JP5 – SW (right-hand side) MUST be in the ON
position. ISO (left-hand side) controls the isolated
supply. See Connections section.
JP6 – VCCA control. See Connections section.
3