TS2508 Taiwan Semiconductor Company, Ltd. (TSC), TS2508 Datasheet - Page 4

• Manufacturer Part Number: TS2508
• Description: 2a / 330khz Pwm Buck Converter
• Manufacturer: Taiwan Semiconductor Company, Ltd. (TSC)

Function Descriptions (Continue)
Setting the Output Voltage
Application circuit item shows the basic application circuit with TS2508 adjustable output version. The external resistor
sets the output voltage according to the following equation:
Table 1: Resistor select for output voltage setting
The R2 setting 5.6k that no load current can be reduce to under 4mA for EL CAP
Input Capacitor Selection
This capacitor should be located close to the IC using short leads and the voltage rating should be approximately 1.5
times the maximum input voltage. The RMS current rating requirement for the input capacitor of a buck regulator is
approximately 1⁄2 the DC load current. A low ESR input capacitor sized for maximum RMS current must be used. A
220µF low ESR capacitor for most applications is sufficient
Output Capacitor Selection
The output capacitor is required to filter the output and provide regulator loop stability. The important capacitor
parameters are; the 100KHz Equivalent Series Resistance (ESR), the RMS ripples current rating, voltage rating, and
capacitance value. For the output capacitor, the ESR value is the most important parameter. The ESR can be
calculated from the following formula.
An aluminum electrolytic capacitor's ESR value is related to the capacitance and its voltage rating. In most case, higher
voltage electrolytic capacitors have lower ESR values. Most of the time, capacitors with much higher voltage ratings
may be needed to provide the low ESR values required for low output ripple voltage. It is recommended to replace this
low ESR capacitor by using a 330µF low ESR values < 130mΩ
Inductor Selection
For most designs, the operate with inductors of 12µH to 33µH. The inductor value can be derived from the following
equation:
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 15% of the maximum load current 2A, ∆IL=0.3A. 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 (2A+0.15A).
3.3V
2.5V
1.8V
1.5V
1.2V
V
5V
1V
OUT
V
RIPPLE
= ∆I
L
1.3K
5.6K
1.5K
5.6K
2.2K
5.6K
1.2K
2.2K
x ESR = 0.33A x 130mΩ = 43mV
R2
2K
2K
6.8K
4.7K
4.7K
1.5K
0.5K
30K
18K
12K
R1
2K
1K
4/8
2A / 330KHz PWM Buck Converter
TS2508
Version: B07