evm6435 Semtech Corporation, evm6435 Datasheet - Page 24

• Manufacturer Part Number: evm6435
• Description: Per-pin Electronics Companion
• Manufacturer: Semtech Corporation

Current Outputs
The TEST_MODE and DAC_OUT pins on the Edge6435/
6436 are used in the same way as for voltage outputs.
The scan circuits for current outputs are shown in Figure
13.
The voltage measured at the DAC_OUT pin, using the
configuration in Figure 13, for Group C and D current
outputs are as follows:
TEST AND MEASUREMENT PRODUCTS
Circuit Description (continued)
2006 Semtech Corp. / Rev. 3, 8/25/06
TEST_MODE
V
V
DAC_OUT_D
DAC_OUT
DAC_OUT_C
where:
R
R
where:
R
R
SENSE_C
PAD
SENSE_D
PAD
DECODER
ADDRESS
= (R
= (R
= 30
= 30
SENSE_C
SENSE_D
= 160
= 160
and
IDAC
NOTE: WHEN ADDRESS 64 IS INVOKED (PARALLEL LOAD), SCAN IS DISABLED.
30%
30%
Figure 13. DAC Current Output vs DAC_OUT
+ R
+ R
+
–
PAD
PAD
30%
30%
) * I
) * I
OUT_C
OUT_D
R
SENSE
IDAC
24
R
PAD
+
–
IOUT_CH0_0
The typical "ON" resistance of the FET switch is 2 k , but
can vary from 900 to 3 k as a function of process and
output voltage.
Notes when Using DAC_OUT Feature with
Multiple Chips
When multiple 6435/6436s are used on a board, and it
is desired to gang the DAC_OUT pins of these 6435/6436s,
or gang the TEST_MODE inputs to one point, it is required
to protect the 6435/6436s against damage that the
following rules be followed:
1)
2)
If TEST_MODE inputs are ganged together,
DAC_OUT cannot be ganged, or invalid results
will be observed at the DAC_OUT pin and damage
could occur to the device. Hence, each DAC_OUT
pin on a 6435/6436 will have to be measured
separately.
If DAC_OUT is ganged, the TEST_MODE is used
to select only one DAC at a time.
R
VIRTUAL GROUND
SENSE
IDAC
CONNECT TO
R
PAD
+
–
IOUT_CH0_1
Edge6435/6436
VIRTUAL GROUND
R
SENSE
CONNECT TO
R
PAD
IOUT_CH0_2
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VIRTUAL GROUND
CONNECT TO