LP5952TL-1.2/NOPB National Semiconductor, LP5952TL-1.2/NOPB Datasheet - Page 11

• Manufacturer Part Number: LP5952TL-1.2/NOPB
• Description: IC REG LDO 1.2V 350MA MICRO5
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LP5952TL-1.2/NOPB

• Regulator Topology: Positive Fixed
• Voltage - Output: 1.2V
• Voltage - Input: Up to 4.5V
• Voltage - Dropout (typical): 0.088V @ 350mA
• Number Of Regulators: 1
• Current - Output: 350mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 5-MicroSMD
• For Use With: LP5952TL-1.2EV - BOARD EVALUATION LP5952TL-1.2
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Limit (min): -
• Other names: LP5952TL-1.2; LP5952TL-1.2TR

Application Hints
DUAL RAIL SUPPLY
The LP5952 requires two different supply voltages:
•V
voltage
•V
It's important that V
the device is used in the typical post regulation application as
shown in Figure 1, the sequencing of the two power supplies
is not an issue as V
and the LP5952. The output voltage of the DC-DC regulator
will take some time to rise up and supply V
this application V
V
In case V
pins will ramp up simultaneously causing no problem.
Only in applications with two independent supplies connected
to the LP5952 special care must be taken to guarantee that
V
POWER DISSIPATION AND DEVICE OPERATION
The permissible power dissipation for any package is a mea-
sure of the capability of the device to pass heat from the power
source, the junctions of the IC, to the ultimate heat sink, the
ambient environment. Thus the power dissipation is depen-
dent on the ambient temperature and the thermal resistance
across the various interfaces between the die and ambient
air.
As stated in the electrical specification section, the allowable
power dissipation for the device in a given package can be
calculated using the equation:
P
With a θ
package returns a value of 1053mW with a maximum junction
temperature of 125°C at T
The actual power dissipation across the device can be esti-
mated by the following equation:
P
BATT
IN
D
D
IN
BATT
= (T
= (V
is always
, the power input voltage, is regulated to the fixed output
.
, the bias input voltage, supplies internal circuitry.
Power Supply Rejection Ratio V
J(MAX)
IN
JA
IN
- V
= 95°C/W, the device in the 5 bump micro SMD
is shorted to V
OUT
- T
≤
V
) * I
A
BATT
) / θ
IN
OUT
IN
BATT
will always ramp up more slowly than
JA
.
does not exceed V
supplies both, the DC-DC regulator
BATT
A
of 25°C or 421mW at T
, the voltages at the two supply
IN
BATT
, 1.5V Option
IN
at any time. If
of LP5952. In
A
of 85°C.
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This establishes the relationship between the power dissipa-
tion allowed due to thermal consideration, the voltage drop
across the device, and the continuous current capability of the
device. These two equations should be used to determine the
optimum operating conditions for the device in the application.
As an example, to keep full load current capability of 350mA
for a 1.5V output voltage option at a high ambient temperature
of 85°C, V
V
Figure 3 shows the output current derating due to these con-
siderations:
The typical contribution of the bias input voltage supply
V
P
EXTERNAL CAPACITORS
As is common with most regulators, the LP5952 requires ex-
ternal capacitors to ensure stable operation. The LP5952 is
specifically designed for portable applications requiring mini-
mum board space and the smallest size components. These
capacitors must be correctly selected for good performance.
IN
BATT
D_VBATT
FIGURE 3. Maximum Load Current vs V
Power Supply Rejection Ratio V
≤
P
to the power dissipation can be neglected:
D
85°C, V
/ I
= V
IN
OUT
has to be kept
BATT
+ V
OUT
* I
OUT
QVBATT
= 1.5V, θ
θ
JA(LLP)
= 421mW / 350mA + 1.5V = 2.7V.
= 5.5V * 50µA = 0.275mW typical.
≤
= 150°C/W,
JA(MICROSMD)
2.7V (for micro SMD package):
BATT
, 1.5V Option
= 95°C/W,
IN
- V
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OUT
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, T
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A
=