TABLE 1. Recommended Output Filter Capacitors

C

Voltage (V), R

Make

Manufacturer

Part Number

Case Size

22

6.3, < 5

Ceramic, X5R

TDK

C3216X5R0J226M

1206

47

6.3, < 5

Ceramic, X5R

TDK

C3216X5R0J476M

1206

47

6.3, < 5

Ceramic, X5R

TDK

C3225X5R0J476M

1210

47

10.0, < 5

Ceramic, X5R

TDK

C3225X5R1A476M

1210

100

6.3, < 5

Ceramic, X5R

TDK

C3225X5R0J107M

1210

100

6.3, 50

Tantalum

AVX

TPSD157M006#0050

D, 7.5 x 4.3 x 2.9 mm

100

6.3, 25

Organic Polymer

Sanyo

6TPE100MPB2

B2, 3.5 x 2.8 x 1.9 mm

150

6.3, 18

Organic Polymer

Sanyo

6TPE150MIC2

C2, 6.0 x 3.2 x 1.8 mm

330

6.3, 18

Organic Polymer

Sanyo

6TPE330MIL

D3L, 7.3 x 4.3 x 2.8 mm

470

6.3, 23

Niobium Oxide

AVX

NOME37M006#0023

E, 7.3 x 4.3 x 4.1 mm

Output Voltage Setting

A resistor divider network from V

the desired output voltage as follows:

R

R

are normally selected as 0.5% or 1% tolerance. Higher accu-

racy resistors such as 0.1% are also available.

The feedback voltage (at V

-2.5% / +2.5% over temperature and over line and load reg-

ulation. Additionally, the LMZ10503EXT contains error nulling

circuitry to substantially eliminate the feedback voltage vari-

ation over temperature as well as the long term aging effects

of the internal amplifiers. In addition the zero nulling circuit

dramatically reduces the 1/f noise of the bandgap amplifier

and reference. The manifestation of this circuit action is that

the duty cycle will have two slightly different but distinct op-

erating points, each evident every other switching cycle.

Loop Compensation

The LMZ10503EXT preserves flexibility by integrating the

control components around the internal error amplifier while

utilizing three small external compensation components from

V

mode compensation network is featured. To ensure stability,

an external resistor and small value capacitor can be added

across the upper feedback resistor as a pole-zero pair to

complete a type III (three pole, two zero) compensation net-

work. The compensation components recommended in Table

2 provide type III compensation at an optimal control loop

performance. The typical phase margin is 45° with a band-

width of 80 kHz. Calculated output capacitance values not

listed in Table 2 should be verified before designing into pro-

duction. A detailed application note is available to provide

verification support, AN-2013. In general, calculated output

capacitance values below the suggested value will have re-

duced phase margin and higher control loop bandwidth. Out-

put capacitance values above the suggested values will

experience a lower bandwidth and increased phase margin.

Higher bandwidth is associated with faster system response

to sudden changes such as load transients. Phase margin

changes the characteristics of the response. Lower phase

margin is associated with underdamped ringing and higher

phase margin is associated with overdamped response. Los-

ing all phase margin will cause the system to be unstable; an

optimized area of operation is 30° to 60° of phase margin, with

a bandwidth of 100 kHz ±20 kHz.

30118248

TABLE 2. LMZ10503EXT Compensation Component

Values

V

IN

(V)

C

ESR (m

Ω)

R

fbt

(k

Ω)

C

comp

(pF)

R

comp

(k

Ω)

Min

Max

5.0

22

2

20

143

39

8.06

47

2

20

100

100

8.25

100

1

10

71.5

180

4.32

150

1

5

56.2

270

2.1

150

10

25

59

270

10.8

150

26

50

66.5

270

23.7

220

15

30

53.6

360

14

220

31

60

59

360

30.1

3.3

22

2

20

100

56.2

5.62

47

2

20

66.5

150

5.49

100

1

10

45.3

270

2.8

150

1

5

40.2

360

1.5

150

10

25

40.2

360

7.32

150

26

50

43.2

360

15.4

220

15

30

40.2

470

10.5

220

31

60

40.2

470

20.5

Note: In the special case where the output voltage is 0.8V, it is recom-

mended to remove R

compensation.

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