Datasheet
OUTA
ON min
IN max SW
V
3.3 V
t 275 ns
V f 30 V 400 kHz
= = =
´ ´
I Pk
I Pk
2
BOOSTFET Pk DS(on) r f SW
2
BOOSTFET
V I
2
V I
P (I ) r (1 TC) D (t t ) f
2
P (7.85 A) 0.02 (1 0.4) 0.53 (20 ns 20 ns) 200 kHz 1.07 W
´
´ ´ ´ ´ ´
´
æ ö
= ´ + ´ + ´ + ´
ç ÷
ç ÷
è ø
æ ö
= W + + + =
ç ÷
è ø
D D(PEAK) F
INMIN
OUT F
D
P I V (1 D)
V
5 V
D 1 1 0.53
V V 10 V 0.6 V
P 7.85 A 0.6 V (1 0.53) 2.2 W
= ´ ´ -
= - = - =
+ +
= ´ ´ - =
TPS43330-Q1
TPS43332-Q1
SLVSA82E –MARCH 2011–REVISED APRIL 2013
www.ti.com
Output Schottky Diode D1 Selection
Maximizing efficiency requires a Schottky diode with low forward-conducting voltage V
F
over temperature and
fast switching characteristics. The reverse breakdown voltage should be higher than the maximum input voltage,
and the component should have low reverse leakage current. Additionally, the peak forward current should be
higher than the peak inductor current. The following calculation gives the power dissipation in the Schottky diode:
Low-Side MOSFET (BOT_SW3)
The times t
r
and t
f
denote the rising and falling times of the switching node and relate to the gate-driver strength
of the TPS43330-Q1, TPS43332-Q1, and gate Miller capacitance of the MOSFET. The first term denotes the
conduction losses, which the low on-resistance of the MOSFET minimizes. The second term denotes the
transition losses which arise due to the full application of the input voltage across the drain-source of the
MOSFET as it turns on or off. Transition losses are higher at high output currents and low input voltages (due to
the large input peak current) and when the switching time is low.
Note: The on-resistance, r
DS(on)
, has a positive temperature coefficient, which produces the (TC = d × ΔT) term
that signifies the temperature dependence. (Temperature coefficient d is available as a normalized value from
MOSFET data sheets and can have an assumed starting value of 0.005 per °C.)
BuckA Component Selection
BuckA Component Selection
t
ON min
is higher than the minimum duty cycle specified (100 ns typical). Hence, the minimum duty cycle is
achievable at this frequency.
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