ATE Contact Test thru analog Switch - IC

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ATE Contact Test thru’ Analog Switch
Conventional ATE Contact Test
CASE#1
CASE#2
• DUT pin is only connected to
the ATE on the loadboard
• Force current -200ua on the
DUT pin
• Measure voltage on the DUT
pin
ATE_CH-xxx
• DUT pin needs to be connected
to the ATE and Support IC as
well for other functional testing
• Use a mechanical relay to
switch between ATE and
Support IC
• Force current -200ua on the
DUT pin
• Measure voltage on the DUT
pin
ATE_CH-xxx
Rly
DUT
DUT
Support IC
Relays
• Advantages
– Low contact resistance – ~<0.5 ohms
– ATEs can easily control them
– Higher bandwidth
• Issues
–
–
–
–
Bulky
Expensive
Mounting it and reworking it on the board when surface mounted
Takes real estate on the board
Analog Switches
• Alternate solution to relays are analog switches
• Pros
–
–
–
–
Small footprint, one IC can switch many DUT pin
Easy manufacturability and rework
Low cost
High Bandwidth
• Issues
– Higher ‘ON’ resistance
– Pose problem in doing ATE contact test due to their own clamp diodes
– Need extra ATE supplies to power them
Analog Switches – No Issues
• Higher ‘ON’ resistance
– With good selection of a switch, this can be tolerated
• Need extra ATE supplies to power them
– Modern ATEs have many power supplies to power the analog switch
• Pose problem in doing ATE contact test due to their own clamp
diodes
– This can be alleviated by skewing the power supplies of the switch
Regular Functional Test
Supporting IC
ATE_CH-xxx
With the analog switch
supplies at 3.3v/0.0v, the
switch’s Ain pins will
connect to either Aout-A or
Aout-B and both the clamp
diodes on the switch’s pins
will act as clamps during
functional testing of the
DUT thru the ATE or
Receiver IC
3.3v
Aout-B
Regular
VDD/VSS
Aout-A
Ain
SEL
0v
Regular IO
control voltage
for Mux control
Vil = 0v
Vih=3.3v
DUT
Contact Test
Supporting IC
ATE_CH-xxx
1.3v
Aout-B
Skewed
VDD/VSS
Aout-A
Ain
SEL
With the analog switch
supplies at 1.3v/-2.0v, the
switch’s Ain pin will be
connected to Aout-A and
both the clamp diodes of
the switch’s pins will be
reverse biased during
contact test of the DUT
pins thru the ATE
-2v
Skewed IO
control voltage
for Mux control
Vil = -2v
Vih=1.3v
DUT
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