TS3420

2A, 1.25MHz Synchronous Buck Converter

4/9

Version: A12

Application Information

Setting the Output Voltage

Application circuit item shows the basic application circuit with TS3410 adjustable output version. The external

resistor sets the output voltage according to the following formula:

Inductor Selection

For most designs, the TS3410 operates with inductors of 2.2µH to 3.3µH. Low inductance values are physically

smaller but require faster switching, which results in some efficiency loss. The inductor value can be derived from

the following formula:

Where is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high

ripple currents. Choose inductor ripple current approximately 20% of the maximum load current 2A, ∆IL=400mA.

For output voltages above 2.0V, when light-load efficiency is important, the minimum recommended inductor is

2.7µH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the 50m

Ω

to 150m

Ω range. For higher efficiency at heavy loads (above 200mA), or minimal load regulation (but some

transient overshoot), the resistance should be kept below 100m

Ω. The DC current rating of the inductor should be

at least equal to the maximum load current plus half the ripple current to prevent core saturation (2000mA+200mA)

Input Capacitor Selection

The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input

capacitor impedance at the switching frequency shall be less than input source impedance to prevent high

frequency switching current passing to the input. A low ESR input capacitor sized for maximum RMS current must

be used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and

small temperature coefficients. A 10µF ceramic capacitor for most applications is sufficient.

Output Capacitor Selection

The output capacitor is required to be 10uF×2 to keep the output voltage ripple small and to ensure regulation loop

stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R

or X7R dielectrics are recommended due to their low ESR and high ripple current

Compensation Capacitor Selection

The compensation capacitors for increasing phase margin provide additional stability. It is required and more than

27pF. Please refer to demo board schematic for design.

Table 1: Resistor Select for Output Voltage Setting

VOUT

R2

R1

1.2V

300K

300K

1.5V

300K

450K

1.8V

300K

600K

2.5V

150K

470K

3.3V

120K

540K

VOUT

1.2V

1.5V

1.8V

2.5V

Inductor

2.7uH

2.7uH

2.7uH

2.2uH

Part Number

WE-TPC

7440430027

7440430027

7440430027

7440430022

Note: Part Type MH or M (www.we-online.com)