0

1.0

2.0

3.0

4.0

5.0

DC BIAS (V)

100%

80%

60%

40%

20%

0402, 6.3V, X5R

0603, 10V, X5R

V

PP-RMS

=

V

PP-C

PP-ESR

2

LM3686

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SNVS520E – AUGUST 2008 – REVISED MAY 2013

Because these two components are out of phase, the rms (root mean squared) value can be used to get an

approximate value of peak-to-peak ripple. The peak-to-peak ripple voltage, rms value can be expressed as

follow:

(6)

Note that the output voltage ripple is dependent on the inductor current ripple and the equivalent series

make sure the value used for calculations is at the switching frequency of the part.

The linear regulator is designed specifically to work with very small ceramic output capacitors. A ceramic

capacitor (dielectric types X7R, Z5U, or Y5V) in the 2.2 µF range (up to 10 µF) and with an ESR between 3 m

Ω

to 300 m

are not as attractive for reasons of size and cost (see Table 2).

A ceramic capacitor in the 1 uF to 2.2 uF range, and with ESR between 5 m

Ω to 500 mΩ, is suitable for the

Figure 24. Graph Showing a Typical Variation In Capacitance vs. DC Bias

Table 2. Suggested Capacitors and their Suppliers

Capacitance / µF

Model

Voltage Rating

Vendor

Type

Case Size / Inch (mm)

10.0

C1608X5R0J106K

6.3V

TDK

Ceramic, X5R

0603 (1608)

4.7

C1608X5R0J475

6.3V

TDK

Ceramic, X5R

0603 (1608)

2.2

C1608X5R0J225M

6.3V

TDK

Ceramic, X5R

0603 (1608)

1.0

C1005JB0J105KT

6.3V

TDK

Ceramic, X5R

0402 (1005)

DSBGA Package Assembly And Use

Use of the DSBGA package requires specialized board layout, precision mounting and careful re-flow

techniques, as detailed in the TI AN-1112 Application Report (SNVA009). Refer to the section "Surface Mount

Technology (SMD) Assembly Considerations". For best results in assembly, alignment ordinals on the PC board

should be used to facilitate placement of the device. The pad style used with DSBGA package must be the

NSMD (non-solder mask defined) type. This means that the solder-mask opening is larger than the pad size.

This prevents a lip that otherwise forms if the soldermask and pad overlap, from holding the device off the

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