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L6910A L6910

Output Capacitor

In the demo 5 POSCAP capacitors, model 6TPB330M, are used, with a maximum ESR equal to 40m

Ω each.

Therefore the resultant ESR is of 8m

Ω. For load transient of 8A in the worst case the voltage drop is of:

The voltage drop due to the capacitor discharge during load transient, considering that the maximum duty cycle

is equal to 100% results in 16.4mV with 1.2V of programmed output.

Input Capacitor

capacitors 20SA100M, with a maximum ESR equal to 30m

Ω, are chosen to sustain the ripple. Therefore, the

resultant ESR is equal to 30m

Ω/3 = 10mΩ. So the losses in worst case are:

P = ESR ·

= 160mW

Over-Current Protection

The peak current is in this case equal to 12A, substituting the demo board parameters in the relationship report-

Efficiency

Figure 12 shows the measured efficiency versus load current for different values of output voltage. The measure

voltage is of 12V.

In the application one mosfets STS12NF30L (30V, 10m

high side.

Since the board has been layed out with the possibility to use up to three SO8 mosfets for both high and low

side switch, to increase efficiency at low output voltages, an additional mosfet on the low side can be considered

because of the duty cycle.

Table 1. Part List

R2

10k

SMD 0805

R3

4.7k

1%

SMD 0805

R5

47k

SMD 0805

R6

10

SMD 0805

R7

620

SMD 0805

R10

14k

E96 1%

SMD 0805

R11

6.98k

E96 1% (optional)

SMD 0805

R12

2.61k

E96 1% (optional)

SMD 0805

R13

1.74k

E96 1% (optional)

SMD 0805

C1

100

µ

OSCON - 20SA100M

Radial 10x10.5mm

C4…C11

330

µ

POSCAP - 6TPB330M

SMD 7343

C12, C13, C15, C21

100n

Ceramic

SMD 0805

C14

1n

Ceramic

SMD 0805

C19

56n

Ceramic

SMD 0805

L1

1.5

µ

T44-52 Core, 7T-18AWG

L2

4.2

µ

SUMIDA CEE125 series

U1

L6910

STMicroelectronics

SO16 NARROW

Q1, Q4

STS12NF30L

STMicroelectronics

SO8

D1

1N4148

STMicroelectronics

SOT23

D2

STPS3340U

STMicroelectronics

SMB

F1

251015A-15°

Littlefuse

AXIAL

I

rm s

2