LP2952IM National Semiconductor, LP2952IM Datasheet - Page 13

• Manufacturer Part Number: LP2952IM
• Description: IC ADJ LDO REG 1.23V TO 29V 250mA 16-SOIC
• Manufacturer: National Semiconductor

Specifications of LP2952IM

• Primary Input Voltage: 30V
• Output Voltage Adjustable Range: 1.23V To 29V
• Dropout Voltage Vdo: 470mV
• No. Of Pins: 16
• Output Current: 250mA
• Operating Temperature Range: -40°C To +125°C
• Dc: 05+
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Application Hints
The next parameter which must be calculated is the maxi-
mum allowable temperature rise, T
by using the formula:
where: T
Using the calculated values for T
required value for junction-to-ambient thermal resistance,
θ
The heatsink is made using the PC board copper. The heat
is conducted from the die, through the lead frame (inside the
part), and out the pins which are soldered to the PC board.
The pins used for heat conduction are given in Table 1.
Figure 2 shows copper patterns which may be used to
dissipate heat from the LP2952 and LP2953. Table 2 shows
some values of junction-to-ambient thermal resistance (θ
for values of L and W for 1 oz. copper.
LP2952IN, LP2952AIN,
LP2952IN-3.3,
LP2952AIN-3.3
LP2953IN, LP2953AIN,
LP2953IN-3.3,
LP2953AIN-3.3
LP2952IM, LP2952AIM,
LP2952IM-3.3,
LP2952AIM-3.3,
LP2953IM, LP2953AIM,
LP2953IM-3.3,
LP2953AIM-3.3
(J–A)
T
R
(max) = T
, can now be found:
FIGURE 1. P
temperature
T
J
A
(max)
(max) is the maximum ambient temperature
Part
TABLE 1. Heat Conducting Pins
J
(max) − T
Current/Voltage Diagram
is
TOTAL
the
A
= (V
(max)θ
maximum
16-Pin Surface
IN
14-Pin DIP
16-Pin DIP
(Continued)
Package
− V
Mount
(J–A)
R
R
(max). This is calculated
(max) and P(max), the
OUT
= T
) I
allowable
L
R
01112707
(max)/P(max)
+ (V
4, 5, 12, 13
1, 8, 9, 16
10, 11, 12
IN
3, 4, 5,
Pins
) I
junction
G
J–A
)
13
* For best results, use L = 2H
** 14-Pin DIP is similar, refer to Table 1 for pins designated for
heatsinking.
HEATSINK REQUIREMENTS (Military Temperature
Range Devices)
The
LP2953AMJ is limited by the maximum junction temperature
(+150˚C) and the two parameters that determine how quickly
heat flows away from the die: the ambient temperature and
the junction-to-ambient thermal resistance of the part.
16-Pin DIP
14-Pin DIP
Surface Mount
TABLE 2. Thermal Resistance for Various Copper
Package
maximum
FIGURE 2. Copper Heatsink Patterns
allowable
Heatsink Patterns
L (in.)
1
2
3
4
6
1
2
3
1
2
3
6
4
2
power
H (in.)
0.19
0.19
0.19
0.19
0.19
0.5
1.5
0.5
1.5
0.5
1.5
1
1
1
dissipation
θ
01112708
J–A
www.national.com
70
60
58
66
66
65
51
49
83
70
67
69
71
73
(˚C/W)
for
the