Datasheet

RF[kW] +
1 10
5
ƒ
sw
[kHz]
R1 +
ǒ
V
OUT
* 1.0
Ǔ
R2
R1
+
1.0V
+
R2
VFB
PWM
SwitchingModulator
Co
Lx
VIN
Rs
+
Control
logic
&
Driver
DRVH
DRVL
ESR
RL
Rgv
Gmv
COMP
VREF
+
2.0V
Voltagedivider
Ramp
comp.
+
R1
+
1.0V
+
R2
VFB
PWM
SwitchingModulator
Co
Lx
VIN
Rs
+
Control
logic
&
Driver
DRVH
DRVL
CSP
CSN
ESR
RL
+
Rgc
Rgv
Cc
Gmv
COMP
VREF
Gmc
+
2.0V
Voltagedivider
Error Amplifier
Ramp
comp.
+
TPS51220A
www.ti.com SLUS897E –DECEMBER 2008–REVISED JANUARY 2013
APPLICATION INFORMATION
EXTERNAL PARTS SELECTION
A buck converter using the TPS51220A consists of linear circuits and a switching modulator. Figure 44 and
Figure 45 show basic scheme.
Figure 44. Simplified Current Mode Functional Blocks
Figure 45. Simplified D-CAP Mode Functional Blocks
The external components can be selected by following manner.
1. Determine output voltage dividing resistors. (R1 and R2: shown in Figure 44) using Equation 7 .
(7)
For D-CAP mode, recommended R2 value is from 10kΩ to 20kΩ.
2. Determine switching frequency. Higher frequency allows smaller output capacitances, however, degrade
efficiency due to increase of switching loss. Frequency setting resistor for RF-pin can be calculated by;
(8)
Copyright © 2008–2013, Texas Instruments Incorporated Submit Documentation Feedback 29
Product Folder Links :TPS51220A