16

LTC1266

LTC1266-3.3/LTC1266-5

APPLICATIO S I FOR ATIO

Troubleshooting Hints

Since efficiency is critical to LTC1266 series applications,

it is very important to verify that the circuit is functioning

correctly in both continuous and Burst Mode operation.

The waveform to monitor is the voltage on the timing

capacitor, Pin 6.

voltage should never dip below 2V as shown in Figure 9a.

cally falling to ground for periods of time as shown in

Figure 9b.

If Pin 6 is observed falling to ground at high output

currents, it indicates poor decoupling or improper ground-

ing. Refer to the Board Layout Checklist.

Board Layout Checklist

When laying out the printed circuit board, the following

checklist should be used to ensure proper operation of the

LTC1266 series. These items are also illustrated graphi-

cally in the layout diagram of Figure 10. Check the follow-

ing in your layout:

1. Are the signal and power grounds segregated? The

LTC1266 signal ground (Pin 12) must return to the

source of the bottom-side MOSFET, anode of the

have as short lead lengths as possible.

able applications, the resistive divider R1 and R2 must

ground.

Figure 10. LTC1266 Layout Diagram (See Layout Checklist)

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

LTC1266

L

SHUTDOWN

BOLD LINES INDICATE

HIGH CURRENT PATHS

OUTPUT DIVIDER REQUIRED WITH

ADJUSTABLE VERSION ONLY

PGND

TDRIVE

PINV

BINH

BDRIVE

SGND

SHDN

470

Ω

R1

R2

LTC1266 • F10

1000pF

3300pF

CT

+

+

+

–

–

3.3V

0V

3.3V

0V

LTC1266 • F09

(a) Continuous Mode Operation

(b) Burst Mode Operation