AN1723

Application ideas

Doc ID 9553 Rev 4

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slaves.The device can also be synchronized from an external source. In this case, the logic

signal must have a frequency higher than the internal switching frequency of the device (500

kHz).

Figure 22.

Synchronization example

7.5

Compensation network with MLCC (multiple layer ceramic

capacitor) at the output

MLCC with values in the range of 10 µF - 22 µF and rated voltages in the range of 10 V - 25

V are available today at relatively low cost from many manufacturers.

These capacitors have very low ESR values (a few m

Ω), so they are sometimes used for the

output filter to reduce the voltage ripple and the overall size of the application.

However, the very low ESR value affects the compensation of the loop (see Section 5) and

in order to keep the system stable, a more complicated compensation network may be

required. Figure 23 shows an example of a compensation network which stabilizes the

system using ceramic capacitors at the output (the optimum component values depend on

the application).

Figure 23.

MLCC compensation network example

AM11329v1

VCC

GND

OUT

FB

INH

SYNC

VREF

1

3

7

5

6

4

8

2

L5973AD

COMP

VCC

GND

OUT

FB

INH

SYNC

VREF

1

3

7

5

6

4

8

2

L5973AD

COMP

VIN

AM11330v1

L1

VIN=5V

C1

MLCC

10uF

D1

STPS340U

Vcc

COMP

GND

OUT

FB

INH

SYNC

VREF

1

3

7

5

6

4

8

2

R3=2.2K

4.7uH

Coilcraft

C4=4.7nF

C2

MLCC

22uF

6.3V

L5973AD

VOUT=2.1V

C5=2.7nF

R4=470

R1=3.3K

C3=220pF

R2=4K7

L1

VIN=5V

C1

MLCC

10uF

D1

STPS340U

Vcc

COMP

GND

OUT

FB

INH

SYNC

VREF

1

3

7

5

6

4

8

2

R3=2.2K

4.7uH

Coilcraft

C4=4.7nF

C2

MLCC

22uF

6.3V

L5973AD

VOUT=2.1V

C5=2.7nF

R4=470

R1=3.3K

C3=220pF

R2=4K7