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LM2637 Datasheet(PDF) 3 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
Part # LM2637
Description  Motherboard Power Supply Solution with a 5-Bit Programmable Switching Controller and Two Linear Regulator Controllers
PDF  17 Pages
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Manufacturer  NSC [National Semiconductor (TI)]
Direct Link  http://www.national.com
Logo NSC - National Semiconductor (TI)

LM2637 Datasheet(HTML) 3 Page - National Semiconductor (TI)

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Electrical Characteristics (Continued)
V
CC = 5V, VDD = 12V unless otherwise specified. Typicals and limits appearing in plain type apply for TA = TJ = +25˚C. Limits
appearing in boldface type apply over the 0˚C to +70˚C range.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
SWITCHING SECTION
I
OVP
OVP Pin Source Current
OVP = 3V
10
mA
GA
Error Amplifier DC Gain
76
dB
B
WEA
Error Amplifier Unity Gain
Bandwidth
5
MHz
V
RAMP_L
Ramp Signal Valley Voltage
1.25
V
V
RAMP_H
Ramp Signal Peak Voltage
3.25
V
t
SS
Soft Start Time
4096
Clock
Cycles
D
STEP_SS
Duty Cycle Step Change in
Soft Start
12.5
%
1.5V LDO CONTROLLER SECTION
V
SNS2
SNS2 Voltage
V
DD = 12V, VCC = 4.75V to
5.25V, I
G2 = 0mAto20mA
(
Figure 1)
1.463
1.5
1.538
V
R
OUT2
Output Resistance
200
Ω
I
SNS2
SNS2 Pin Bias Current
When Regulating
21
µA
V
PWGD_HI
PWGD High Trip Point
(Note 4)
0.63
V
V
PWGD_LO
PWGD Low Trip Point
(Note 4)
0.44
V
2.5V LDO CONTROLLER SECTION
V
SNS3
SNS3 Voltage
V
DD = 12V, VCC = 4.75V to
5.25V, I
G3 = 0mAto20mA
(
Figure 1)
2.438
2.5
2.563
V
R
OUT3
Output Resistance
200
Ω
I
SNS3
SNS3 Pin Bias Current
When Regulating
21
µA
V
PWGD_HI
PWGD High Trip Point
(Note 4)
0.63
V
V
PWGD_LO
PWGD Low Trip Point
(Note 4)
0.44
V
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating ratings are conditions under which the device operates
correctly. Operating Ratings do not imply guaranteed performance limits.
Note 2: Maximum allowable power dissipation is a function of the maximum junction temperature, TJMAX, the junction-to-ambient thermal resistance, θJA, and the
ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PMAX = (TJMAX −TA)/θJA. The
junction-to-ambient thermal resistance,
θJA, for LM2637 is 78˚C/W. For a TJMAX of 150˚C and TA of 25˚C, the maximum allowable power dissipation is 1.6W.
Note 3: The letter
N stands for the typical output voltages appearing in italic boldface type in Table 1.
Note 4: The output level of the PWGD pin is a logic AND of the power good function of the switching section, the 1.5V section and the 2.5V section.
www.national.com
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