TPS64200,TPS64201

TPS64202,TPS64203

SLVS485 − AUGUST 2003

www.ti.com

22

Ceramic Output Capacitor

SW

CDRH6D28-100

Si5475DC

MBRM120LT3

EN

GND

FB

VIN

ISENSE

5 V

CI

10

µF

TPS64203

R1a

680 k

Ω

R2

300 k

Ω

Cff

82 pF

Co

22

µF X5R

6.3 V

3.3 V / 2 A

R1b

2.2 M

Ω

R(ISENSE) = 33 mΩ

R(GATE)

10

Ω

1

2

3

6

5

4

10

µH

Figure 27. Application Using a Ceramic Output Capacitor

The control scheme of the TPS6420x usually requires an output capacitor with some tens of milliohms of ESR

for stability, which is usually the case for tantalum capacitors. This application circuit above also works with

ceramic capacitors. Resistor R1b is used to add an additional control signal to the feedback loop, which is

coupled into the FB pin. The circuit works best with R1b = 2

…4 x R1a. If the resistance of R1b is too low

compared to R1a, the more load regulation the output voltage shows, but stability is best. The advantage of

this circuit is a very low output voltage ripple and small size. The gate resistor shown can be used in every

application. It minimizes switching noise of the converter and, therefore, increases stability and provides lower

output voltage ripple. However, it decreases efficiency slightly because the rise and fall time, and the associated

losses are larger.

(28)

R1

+

1

1

R1a

) 1

R1b

R1b

+

1

1

R1

– 1

R1a

Use the following equation to calculate R1a if R1b = 4R1a

R1a

+ 5

4

R1

(29)