LM3205TLEV National Semiconductor, LM3205TLEV Datasheet - Page 14

• Manufacturer Part Number: LM3205TLEV
• Description: BOARD EVALUATION LM3205TL
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3205TLEV

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 0.8 ~ 3.6V
• Current - Output: 650mA
• Voltage - Input: 2.7 ~ 5.5V
• Regulator Topology: Buck
• Frequency - Switching: 2MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM3205
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -

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form 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 de-
signed for mobile phones where the system controller con-
trols operation mode for maximizing battery life and require-
ments for small package size outweigh the additional size
required for inclusion of UVLO (Under Voltage Lock-Out) cir-
cuitry.
microSMD PACKAGE ASSEMBLY AND USE
Use of the microSMD package requires specialized board
layout, precision mounting and careful re-flow techniques, as
detailed in National Semiconductor Application Note 1112.
Refer to the section Surface Mount Technology (SMD) As-
sembly Considerations. For best results in assembly, align-
ment ordinals on the PC board should be used to facilitate
placement of the device. The pad style used with microSMD
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 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 cor-
14
ners. 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 sol-
ders 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, in-
adequate thermal relief’s can result in late or inadequate re-
flow of these bumps.
The microSMD package is optimized for the smallest possible
size in applications with red or infrared opaque cases. Be-
cause the microSMD package lacks the plastic encapsulation
characteristic of larger devices, it is vulnerable to light. Back-
side 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,
microSMD devices are sensitive to light, in the red and in-
frared range, shining on the package’s exposed die edges.
LLP PACKAGE ASSEMBLY AND USE
Use of the LLP package requires specialized board layout,
precision mounting and careful re-flow techniques, as de-
tailed in National Semiconductor Application Note 1187. Re-
fer 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 place-
ment of the device and must attach to the DAP(Die Attach
Pad) of the LLP package. The pad style used with LLP pack-
age 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 for specific instructions how to do this.