Datasheet

TS2581
PWM Controller
4/7 Version: A11
Application Information
Setting the Output Voltage
Application circuit item shows the basic application circuit with adjustable output version. The external resistor sets
the output voltage according to the following formula:
V
OUT
= 1.0V × (1+
6R
3R
)
Table 1 Resistor select for output voltage setting
V
OUT
R6 R3
5.0V 3K 12K
3.3V 3K6 8K2
Current Limit Protection
The Current limit is set by outside resistance (R
SENSE
), When the S
ENSE
pin voltage larger than 110mV, the current
limit is happened that driver can be turned off until small than 90mV. The current limit set according to the following
formula:
SENSE
R
mV110
(A)Limit Current =
The maximum output current table is shown as below; please refer the table to design.
R
SENSE
(Ω) Current Limit (A) Maximum Output Current (A)
25m 4.4 4.1
30m 3.66 3.3
50m 2.2 1.9
75m 1.46 1.1
Inductor Selection
For most designs, the different frequency can be reducing the inductor value; The TS2581 is suggested 22µH to
100µH for 100K to 300KHz frequencies. Please refer the below table to design.
L1 recommend value (V
IN
=10~30V ,V
OUT
=5V, I
OUT
=2A)
L1 Value (H) 68~100uF
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 3A, ∆IL=0.6A. 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 (3A+0.3A).
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 220~470µF low ESR capacitor for most applications is sufficient.