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4.5
Internal Reference Operation
IOUT
FS
+
16
ǒ
V
EXTIO
R1
Ǔ
4.6
External Reference Operation
Circuit Description
The full-scale output current is set by applying an external resistor (R1) between the BIASJ pin of the
DAC5687 device and ground. The full-scale output current can be adjusted from 20 mA down to 2 mA by
varying R1 or changing the externally applied reference voltage. The full-scale output current, IOUTFS, is
defined as follows:
where VEXTIO is the voltage at pin EXTIO. This voltage is 1.2 V typical when using the internally provided
bandgap reference voltage source.
The internal reference can be disabled and overridden by an external reference by connecting a voltage
source to EXTI/O and connecting EXTLO to +3.3VA (jumper W1 installed between pins 1 and 2). The
specified range for external reference voltages must be observed (see the DAC5687 data sheet
(
) for details).
SLWU017B – APRIL 2005 – Revised March 2007
DAC5687 EVM
25
