LM3205

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SNVS388E – JULY 2005 – REVISED APRIL 2013

Table 2. Suggested capacitors and their suppliers

Model

Vendor

0805ZD475KA 4.7µF, 10V

AVX

C1608X5R0J475M, 4.7µF, 6.3V

TDK

C2012X5R0J106M,10µF, 6.3V

TDK

The input filter capacitor supplies AC current drawn by the PFET switch of the LM3205 in the first part of each

cycle and reduces the voltage ripple imposed on the input power source. The output filter capacitor absorbs the

AC inductor current, helps maintain a steady output voltage during transient load changes and reduces output

voltage ripple. These capacitors must be selected with sufficient capacitance and sufficiently low ESR

(Equivalent Series Resistance) to perform these functions. The ESR of the filter capacitors is generally a major

factor in voltage ripple.

EN PIN CONTROL

Drive the EN pin using the system controller to turn the LM3205 ON and OFF. Use a comparator, Schmidt trigger

or logic gate to drive the EN pin. Set EN high (>1.2V) for normal operation and low (<0.5V) for a 0.01µA (typ.)

shutdown mode.

Set EN low to turn off the LM3205 during power-up and under voltage conditions when the power supply is less

than the 2.7V minimum operating voltage. The part is out of regulation when the input voltage is less than 2.7V.

The LM3205 is designed for mobile phones where the system controller controls operation mode for maximizing

battery life and requirements for small package size outweigh the additional size required for inclusion of UVLO

(Under Voltage Lock-Out) circuitry.

DSBGA PACKAGE ASSEMBLY AND USE

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

techniques, as detailed in TI Application Note 1112 (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 solder-mask and pad overlap, from holding the device off the surface of the board

and interfering with mounting. See Application Note 1112 (SNVA009) for specific instructions how to do this.

The 8-Bump package used for LM3205 has 300micron solder balls and requires 10.82mil pads for mounting on

the circuit board. The trace to each pad should enter the pad with a 90°entry angle to prevent debris from being

caught in deep corners. Initially, the trace to each pad should be 7mil wide, for a section approximately 7mil long,

as a thermal relief. Then each trace should neck up or down to its optimal width. The important criterion is

symmetry. This ensures the solder bumps on the LM3205 re-flow evenly and that the device solders level to the

board. In particular, special attention must be paid to the pads for bumps A1, A3 and B3. Because PGND and

PVIN are typically connected to large copper planes, inadequate thermal relief’s can result in late or inadequate

re-flow of these bumps.

The DSBGA package is optimized for the smallest possible size in applications with red or infrared opaque

cases. Because the DSBGA package lacks the plastic encapsulation characteristic of larger devices, it is

vulnerable to light. Backside metallization and/or epoxy coating, along with front-side shading by the printed

circuit board, reduce this sensitivity. However, the package has exposed die edges. In particular, DSBGA

devices are sensitive to light, in the red and infrared range, shining on the package’s exposed die edges.

WSON PACKAGE ASSEMBLY AND USE

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

as detailed in TI Application Note 1187 (SNOA401). Refer to the section Surface Mount Technology (SMT)

Assembly Recommendations. For best results in assembly, alignment ordinals on the PC board should be used

to facilitate placement of the device and must attach to the DAP(Die Attach Pad) of the WSON package. The pad

style used with WSON 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 solder-mask and pad

overlap, from holding the device off the surface of the board and interfering with mounting. See Application Note

1187 (SNOA401) for specific instructions how to do this.

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