AN1280 - APPLICATION NOTE

4/8

Proper operation of this step-up converter is guar-

anteed at as low as 2.7V with a rise time (0 to 90%

of V(C

is the worst case. At 5V, the rise time of V(C

is 250

µs typ. The C

power ON under 5V supply voltage is shown on

figure 6.

Figure 6 : Step Up Converter Rise Time

Trace 1 represents the power supply voltage (0 to

5V).

Trace 2 represents the C

ON (0 to 5+13,4 = 18,4V).

Table (a) summerizes the recommended values

of the C

charge and low ripple voltage with their corre-

sponding maximum current surge (I

common power supply values. For each power

supply value is also given the recommended value

of a bypass capacitor (C

on the power sup-

plies.

Note that both C

surface mount packages.

Table (a) : Recommended values for C

L

BOOST

2.4. Single Supply Breaker Application

The TD230 is perfectly suited to fit in single sup-

plied applications (ex 0-5V), and can drive only

one power MOSFET used as high side power

switch.

Figure 7 shows how TD230 can be used as a sin-

gle circuit breaker with the same performances.

Figure 7 : Single Electronic Circuit Breaker

Application

In this case, the external components consist in

one boost inductor, one sense resistor, three ca-

pacitors, and one power MOSFET.

2.5. Typical Telecom Line Cards Protection

Application

One of the typical applications where the TD230

can display all its technical advantages is in an ex-

change Telecom Cards protection. Sometimes fif-

ty cards or more are to be supplied with the same

power supply (+/-5V, 1kW), and a decentralized

protection is needed because one card may be

faulty, but should not penalize the others with un-

adapted protection system. The risk of complete

breakdown of the system must be eradicated.

In this application the two above described over

current causes (external line perturbation or inter-

nal component fault) are likely to happen. In the

first case, the current limitation on each card will

ensure undammaging on-board conditions, and in

the second case, the faulty card will be disjoncted

from the power supply until reset.

Figure 8 shows a typical telecom application with

decentralized protection.

In this application, the positive power supply

serves the logic control and analog signals where-

as the negative power supply is dedicated to the

analog.

V

CC

+

V

nF

µH

mA

mV

mA

µF

2.7

47

100

68

60

190

100

5>1

5

100

220

35

120

2.5

1

10

100

220

470

33

220

100

2.2

1

12

220

470

39

150

2.2

1

14

220

680

34

150

2.4

1

18

220

1000

31

200

2.7

1

1

2

3

4

5

6

7

8

Vcc+

GND

LBOOS T

C TRIP1

CBOOST

9

10

11

12

13

14

15

16

CONTROL

PVcc

LBOOST

CBOOST

PM1

GND

PM2

O SCGND

NVcc

REF1

GC1

SENS P

INHIBIT

SHUTDOWN

S E NSN

GC2

REF2

RS 1

NMos

to BOARD

C SS1