Data Sheet

LT8641A

analog.com

Rev 0

21 of 35

(47b)

Figure 47. SW Frequency vs Load Information in Burst Mode Operation (47a) and Pulse-Skipping Mode (47b)

Figure 48. Burst Mode Operation

For some applications, it is desirable for the LT8641A to operate in pulse-skipping mode, offering two major dif-

ferences from Burst Mode operation. First is the clock stays awake at all times and all switching cycles are aligned to

the clock. In this mode, much of the internal circuitry is awake at all times, increasing quiescent current to several

hundred μA. Second is that full switching frequency is reached at lower output load than in Burst Mode operation

(see Figure 47). To enable pulse-skipping mode, float the SYNC/MODE pin. When a clock is applied to the SYNC/MODE

pin, the LT8641A also operates in pulse-skipping mode.

FB Resistor Network

The output voltage is programmed with a resistor divider between the output and the FB pin. Choose the

resistor values according to Equation 1.

R1 = R2 (

VOUT

0.81V

− 1)

(1)

Reference designators refer to the Block Diagram. 1% resistors are recommended to maintain output voltage

accuracy.

FRONT PAGE APPLICATION

VOUT = 5V

fSW = 1MHz

INPUT VOLTAGE (V)

5

15

25

35

45

55

65

0

20

40

60

80

100

120

140

T

10µs/DIV

VSW

5V/DIV

IL

500mA/DIV

FRONT PAGE APPLICATION

12VIN TO 5VOUT AT 10mA

VSYNC = 0V