LM2750LD-5.0 National Semiconductor, LM2750LD-5.0 Datasheet - Page 10

• Manufacturer Part Number: LM2750LD-5.0
• Description: Low Noise/ 5.0V Regulated Switched Capacitor Voltage Converter
• Manufacturer: National Semiconductor

www.national.com
Application Information
cause efficiency is inversely proportional to input voltage, it
is highest when the input voltage is low. In fact, for an input
voltage of 2.9V, efficiency of the LM2750 is greater than 80%
(I
The average efficiency for an input voltage range spanning
the Li-Ion range (2.9V-to-4.2V) is 70% (I
higher input voltages, efficiency drops dramatically. In Li-Ion-
powered applications, this is typically not a major concern,
as the circuit will be powered off a charger in these circum-
stances. Low efficiency equates to high power dissipation,
however, which could become an issue worthy of attention.
LM2750 power dissipation (P
tracting output power from input power:
Power dissipation increases with increased input voltage
and output current, up to 772mW at the ends of the operating
ratings (V
tion self-heats the device. Dissipating this amount power/
heat so the LM2750 does not overheat is a demanding
thermal requirement for a small surface-mount package.
OUT
P
D
≥ 40mA) and peak efficiency is 85% (I
= P
IN
IN
- P
= 5.6V, I
OUT
= [V
OUT
IN
= 120mA). Internal power dissipa-
x (2·I
D
) is calculated simply by sub-
OUT
+ I
Q
)] - [V
OUT
(Continued)
OUT
OUT
= 120mA). At
= 120mA).
x I
OUT
]
10
When soldered to a PCB with layout conducive to power
dissipation, the excellent thermal properties of the LLP pack-
age enable this power to be dissipated from the LM2750 with
little or no derating, even when the circuit is placed in el-
evated ambient temperatures (see Optimizing Layout for
Thermal Dissipation section).
FIGURE 2. LM2750 Model for Power Efficiency and
Power Dissipation Calculations
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