Datasheet

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S001
TPS2500, TPS2501
www.ti.com SLVS886C –OCTOBER 2008–REVISED AUGUST 2010
APPLICATION INFORMATION
Step-by-Step Design Procedure
The following design procedure provides an example for selecting component values for the TPS2500.
The following design parameters are needed as inputs to the design process.
• Input voltage range
• Output voltage on AUX
• Input ripple voltage
• Output ripple voltage on AUX
• Output current rating of AUX rail
• Output current rating of USB rail
• Nominal efficiency target
• Operating frequency
A power inductor, input and output filter capacitors, and current-limit threshold resistor are the only external
components required to complete the TPS2500 boost-converter design. The input ripple voltage, AUX ripple
voltage, and total output current affect the selection of these components.
This design example assumes the following input specifications.
PARAMETER EXAMPLE VALUE
Input voltage range (V
IN
) 2.7 V to 4.2 V
AUX voltage (V
AUX
) 5.1 V (internally fixed)
Input ripple voltage (ΔV
IN
) 15 mV
AUX ripple voltage (ΔV
AUX
) 50 mV
AUX current (I
AUX
) 0.5 A
USB current (I
USB
) 0.5 A
Total current (I
TOTAL
= I
AUX
+ I
USB
) 1 A
Efficiency target, nominal 90%
Switching frequency (f) 1 MHz
Figure 22. Reference Schematic
Switching Frequency
The switching frequency of the TPS2500 is internally fixed at 1 MHz.
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