TPS6734I

FIXED 12-V 120-mA BOOST-CONVERTER SUPPLY

SLVS127A – AUGUST 1995 – REVISED JANUARY 1999

9

POST OFFICE BOX 655303

APPLICATION INFORMATION

The TPS6734 operates in a boost circuit as shown in Figures 1 and 11. Figure 1 shows the typical application

circuit, which generates 12 V from a nominal 5-V source. The circuit is ideal for processor interface for energy

management, because EN can be controlled by logic signals to place the 12-V source into the shutdown mode

(3-

µA current drain) when 12 V is not needed. An example of such an application is a flash memory device that

requires 12 V for the erase cycle.

discontinuous mode

The circuit shown in Figure 1 operates in discontinuous mode over most of the range of input voltage and output

current. In discontinuous mode, current through the inductor begins at zero, rises to a peak value, then ramps

down to zero each cycle as shown by the voltage and current waveforms in Figure 8. The ringing in the voltage

waveform on OUT results from a resonance between the inductor and the power switch capacitance and is

normal for discontinuous operation.

0

02

4

6

8

10

5

15

DISCONTINUOUS MODE

20

12

14

16

18

10

1

0.5

0

t – Time –

µs

VI = 5 V

VO = 12 V

IL = 50 mA

Figure 8