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For external resistor sensing, cut the trace as follows.
Figure 3. (CH1) Cut Trace Underneath R6 Figure 4. (CH2) Cut Trace Underneath R20
5.4 Overcurrent Limit and Discharge Selection
The overcurrent limit threshold and discharge function can be set by the TRIP pin using JP1 on the EVM.
Default setting is 60 mV and discharge enabled.
Table 5. TRIP/ Discharge Mode Selection
Jumper (JP2) set to TRIP VOCL Discharge
Top (1-2 pin shorted) GND 31 mV Enabled
Second (3-4 pin shorted) VREF2 31 mV Disabled
Third (5-6 pin shorted) VREG3 60 mV Disabled
Bottom (7-8 pin shorted) VREG5 60 mV Enabled
5.5 Control Mode and Protection Selection
The control mode and protection function can be set by the FUNC pin using JP2 on the EVM.
Default setting is current mode and UVP/OVP-enabled.
Table 6. Control Mode/OVP Selection
Jumper (JP2) set to FUNC Mode OVP
Top (1-2 pin shorted) GND Current Enabled
Second (3-4 pin shorted) VREF2 D-CAP Disabled
Third (5-6 pin shorted) VREG3 D-CAP Enabled
Bottom (7-8 pin shorted) VREG5 Current Disabled
5.6 Soft-Start Setting Selection
Output voltage soft-start time can be set by the ENx pin using some capacitors on the EVM.
Default setting is integrated soft start.
Table 7. Soft-Start Setting Selection
(1)
CH1 (C20) CH2 (C7)
Integrated soft start Open (adding small bypass-capacitor; 100 Open (adding small bypass-capacitor; 100
pF) pF)
External soft start Put on Put on
(1)
When external soft start is selected, add appropriate capacitor on C20 and/or C7.)
6
High-Performance Synchronous Buck EVM Using the TPS51220 SLVU251A–June 2008–Revised May 2011
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