TPS43000_15 Datasheet, PDF (19/32 Pages) Texas Instruments – MULTI-TOPOLOGY HIGH-FREQUENCY

TPS43000
APPLICATION INFORMATION
SLUS489 − OCTOBER 2001
For a boost converter, the average output current is related to the peak inductor current by the following
equation:
Ipk
+
ǒ_VOUT
ǒ_h
IOUT^Ǔ
VIN^Ǔ
)
ǒ_VIN
ǒ_{2 fSW}
D^Ǔ
L^Ǔ
(19)
where f_SW is the switching frequency, L is the inductor value, and D is the duty cycle. The duty cycle for a boost
converter is defined as:
D
+
ǒ_{VOUT * VIN}Ǔ
VOUT
(20)
Note that in these equations the voltage drop across the rectifier has been neglected.
non−synchronous boost converter
The TPS43000 can also be used in non-synchronous applications to provide output voltages greater than 8 V
from low voltage inputs. Figure 6 shows the TPS43000 in a non-synchronous boost converter (750 kHz)
application with an input voltage range of 2.5 V to 9.0 V, an output voltage of 12 V, and a load current from 0
A to 1 A. Since none of the device pins are exposed to the boosted voltage, the output voltage is limited only
by the ratings of the external MOSFET, rectifier, and filter capacitor. At these higher output voltages, good
efficiency is maintained since the rectifier drop is small compared to the output voltage. Note that the PFM mode
can still be used to maintain high efficiency at light load.
Since all the power supply pins (VIN, VOUT, VP) operate off the input voltage, it must be greater than 2.5 V and
high enough to assure proper gate drive to the charge MOSFET.
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