L +

V

V

O

V

IN

DI

f

SW

(Henries)

2

4

6

8

12

10

V

2

1

5

4

6

3

110°C

– 55°C

25°C

2

4

6

8

12

10

V

2

0

8

6

10

4

110°C

– 55°C

25°C

1

7

5

9

3

TPS40054

TPS40055

TPS40057

www.ti.com

SLUS593H – DECEMBER 2003 – REVISED JULY 2012

BP5 AND BP10 INTERNAL VOLTAGE REGULATORS

Start-up characteristics of the BP5 and BP10 regulators over different temperature ranges are shown in Figure 7

and Figure 8. Slight variations in the BP5 occurs dependent upon the switching frequency. Variation in the BP10

regulation characteristics is also based on the load presented by switching the external MOSFETs.

INPUT VOLTAGE

INPUT VOLTAGE

vs

vs

BP5 VOLTAGE

BP10 VOLTAGE

Figure 7.

Figure 8.

SELECTING THE INDUCTOR VALUE

The inductor value determines the magnitude of ripple current in the output capacitors as well as the load current

at which the converter enters discontinuous mode. Too large an inductance results in lower ripple current but is

physically larger for the same load current. Too small an inductance results in larger ripple currents and a greater

number of (or more expensive output capacitors for) the same output ripple voltage requirement. A good

compromise is to select the inductance value such that the converter doesn't enter discontinuous mode until the

load approximated somewhere between 10% and 30% of the rated output. The inductance value is described in

Equation 5.

where

•

•

ΔI is the peak-to-peak inductor current

(5)

Copyright © 2003–2012, Texas Instruments Incorporated

Submit Documentation Feedback

11

Product Folder Link(s): TPS40054 TPS40055 TPS40057