LMZ10505

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SNVS633G – JANUARY 2010 – REVISED APRIL 2013

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In this particular design the output capacitance is determined by the load transient requirements.

Table 1 lists some examples of commercially available capacitors that can be used with the LMZ10505.

Table 1. Recommended Output Filter Capacitors

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

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Resistors are normally selected as 0.5% or 1% tolerance. Higher accuracy resistors such as 0.1% are also

available.

load regulation. Additionally, the LMZ10505 contains error nulling circuitry to substantially eliminate the feedback

voltage variation 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 operating points, each evident

every other switching cycle.

Loop Compensation

The LMZ10505 preserves flexibility by integrating the control components around the internal error amplifier while

zero) voltage-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 network. 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 bandwidth of 80

kHz. Calculated output capacitance values not listed in Table 2 should be verified before designing into

production. A detailed application note is available to provide verification support, AN-2013 (SNVA417). In

general, calculated output capacitance values below the suggested value will have reduced phase margin and

higher control loop bandwidth. Output 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. Losing 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.

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