TS19378
Taiwan Semiconductor
Document Number: DS_P0000199 5 Version: B15
APPLICATION INFORMATION (CONTINUE)
EN/SS
This pin can be supplied shutdown or soft start function. It is inside pull high function. For normal application, the
pin must be connected a capacitor to ground. There is a 5μA current to charge this capacitor, vary the different
capacitor value to control soft start time. Allow the switching regulator circuit to be shutdown pulling this pin below
a 0.8V threshold voltage; the shutdown supply current is approximately 150μA
Inductor Selection
For most designs, the different frequency can be reducing the inductor value; The TS19378 is suggested 33μH.
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, ΔIL=0.4A. 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+0.2A).
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.
Over Voltage Protection
The OVP voltage is set by outside resistance (R1 and R4). The external resistor sets the OVP voltage according to
the following equation:
)
4
1()(
R
VOVPV
OVPOUT
+×=
If V
OVP
>0.85V, The OVP is happened that to disable the driver until V
OVP
<0.85V.
Output Capacitor Selection
For lower output voltage ripple and more stable LED current, higher value output capacitor and low ESR is
recommended. A 470µF electrolytic capacitor works for most of the applications.
