an30888b Panasonic Corporation of North America, an30888b Datasheet - Page 20

• Manufacturer Part Number: an30888b
• Description: High Brightness Led Driver Ic
• Manufacturer: Panasonic Corporation of North America

AN30888B
(3) Internal regulator
An internal 3.65 V regulator is used as the power supply for internal core circuit of this IC.
This regulated voltage, V
will act as a V
depends on load current of the regulator and also tolerance of the IC. In general, the regulator output voltage will be approximately 0.3 V
lower than V
This regulator requires a capacitor of 1 μF to be connected to VREG pin. This capacitor helps to provide a stable regulated voltage to the
IC. The regulator has a current ability of approximately 15 mA. However, it is not designed to provide as external power supply voltage.
Hence an external load exceeding approximately 0.5 mA to the VREG pin is not allowed.
(4) Output setting consideration
The output voltage, V
For Boost mode or Buck-Boost mode operation, V
MOSFET as mention in (11). Also V
For Buck mode operation, V
current setting.
Technical Data (continued)
Functions and properties descriptions (continued)
V
V
V
IN
OUT
OUT
OUT
IN
during this mode of operation.
voltage follower, with output voltage close to V
= (V
= (V
= (V
V
V
N
V
D
IN
F
LEDs
OUT
F
IN
F
:
:
:
× N
× N
– V
REG
: Number of LEDs stacked in series
is set using the following equations for both boost and buck mode:
Battery or Input power supply voltage
LED forward drop voltage
Schottky diode forward drop voltage
LEDs
LEDs
F
OUT
will be provided when V
× N
+ V
+ V
setting should give sufficient voltage for external MOSFET to operate properly at the required output
) N LEDs
* V F
VIN
( V out
− − − =
- -
) * ( N LEDs
VF
VIN
Vout
− =
LEDs
D
D
OUT
) ……………………………………………… Eq[1]
+V
) ……………………………………………… Eq[2]
IN
should be lesser than OVP protection threshold as mentioned in (9).
) ………………………………………… Eq[3]
OUT
IN
setting should be lesser than Drain–Source breakdown voltage of external
is approximately in the range of 4 V to 15V. For V
SDG00005AEB
IN.
The amount of drop voltage from V
(Boost mode)
(Buck mode)
(Buck-Boost mode)
IN
during V
IN
lower than 4 V, regulator
IN
follower mode
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