lm2638m National Semiconductor Corporation, lm2638m Datasheet - Page 3

• Manufacturer Part Number: lm2638m
• Description: Motherboard Power Supply Solution With A 5-bit Programmable Switching Controller And Two Linear Regulator Controllers
• Manufacturer: National Semiconductor Corporation

SWITCHING SECTION
V
V
V
I
V
1.5V LDO CONTROLLER SECTION
V
R
I
V
V
1.25V LDO CONTROLLER SECTION
V
R
I
V
V
CS+
SNS2
SNS3
PWGD_HI
PWGD_LO
OVP_TRP
OCP
SNS2
PWGD_HI
PWGD_LO
SNS3
PWGD_HI
PWGD_LO
Electrical Characteristics
plain type apply for T
Symbol
OUT2
OUT3
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, T
ambient temperature, T
junction-to-ambient thermal resistance,
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 1.25V section. For the switch-
ing section, the power good is a window. For the two linear sections, the power good is a threshold with some hysteresis.
PWGD High Trip Point
PWGD Low Trip Point
Over-Voltage Trip Point
CS+ Pin Sink Current
Over-Current Trip Point (CS+
and CS− Differential Voltage)
SNS2 Voltage
Output Resistance
SNS2 Pin Bias Current
PWGD High Trip Point
PWGD Low Trip Point
SNS3 Voltage
Output Resistance
SNS3 Pin Bias Current
PWGD High Trip Point
PWGD Low Trip Point
A
. The maximum allowable power dissipation at any ambient temperature is calculated using: P
A
= T
Parameter
J
= +25˚C. Limits appearing in boldface type apply over the 0˚C to +70˚C range. (Continued)
JA
, for LM2638 is 78˚C/W. For a T
V
CC
= 5V, V
% Above Rated Output Voltage
When Output Voltage
% Above Rated Output Voltage
When Output Voltage (Note
4)
% Below Rated Output Voltage
When Output Voltage
% Below Rated Output Voltage
When Output Voltage (Note
4)
% SNS1 Above Rated Output
CS+ = 5V, CS− = 4.8V
CS+ = 2V, CS− Drops from 2V
V
5.25V, I
When Regulating
(Note 4)
(Note 4)
V
5.25V, I
When Regulating
(Note 4)
(Note 4)
DD
DD
= 12V, V
= 12V, V
DD
G2
G3
Conditions
JMAX
= 12V unless otherwise specified. Typicals and limits appearing in
= 0 mA to 20 mA
= 0 mA to 20 mA
CC
CC
of 150˚C and T
3
= 4.75V to
= 4.75V to
A
of 25˚C, the maximum allowable power dissipation is 1.6W.
JMAX
, the junction-to-ambient thermal resistance,
1.463
1.219
Min
126
15
41
5
6
11.5
0.63
0.44
1.25
0.63
0.44
Typ
185
200
200
2.6
9.5
1.5
25
55
21
7
0
MAX
= (T
1.538
1.281
JMAX
Max
244
13
13
35
69
9
6
− T
www.national.com
A
JA
)/
, and the
JA
Units
mV
. The
µA
µA
µA
%
%
%
V
V
V
V
V
V