Datasheet

[ ]
8
sw
1 10
= [kHz]
RF
f
´
W
www.ti.com Configuration
Table 1. Switching Frequency Selection
Connection
Add RF-resistor from RF to GND and be R31 open
Internal
Apply external clock signal to SYNC (5 Vpp and 50% duty) , remove R15 in addition, and
External
add 0-Ω to R31.
5.2 Skip Mode and Control Scheme Selection
The skip mode can be set by the SKIPSEL1,2 pins using JP3 and JP4 on the EVM.
Default setting is Auto-skip.
Table 2. Skip Mode Selection
Jumper (JP3, JP4) set to SKIPSEL1,2 Skip
Top (1-2 pin shorted) GND CCM
Second (3-4 pin shorted) VREF2 Auto-skip
Third (5-6 pin shorted) VREG3 OOA (<400-kHz)
Bottom (7-8 pin shorted) VREG5 OOA (>400-kHz)
5.3 Current-Sensing Selection
The current-sensing scheme can be set by the external current sensing devices, using some resistors on
the EVM.
Default setting is Inductor DCR sensing
Table 3. Current-Sensing Scheme Selection (CH1)
R8 R29 R35 R36 R6 R7 R25
Inductor DCR Put on
(1)
Put on
(1)
Put on
(1)
Put on
(1)
Open Open Open
(if necessary)
External Put on
(1)
Put on
(1)
Put on
(1)
Open Put on
(1)
Open Open
Resistor (if necessary) Cut trace
(1)
"Put on” means add appropriate resistor.
Table 4. Current Sensing Scheme Selection (CH2)
R18 R28 R33 R37 R20 R19 R26
Inductor DCR Put on
(1)
Put on
(1)
Put on
(1)
Put on
(1)
Open Open Open
(if necessary)
External Put on
(1)
Put on
(1)
Put on
(1)
Open Put on
(1)
Open Open
Resistor (if necessary) Cut trace
(1)
"Put on” means add appropriate resistor.
5
SLVU251A–June 2008–Revised May 2011 High-Performance Synchronous Buck EVM Using the TPS51220
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