lm2637mx National Semiconductor Corporation, lm2637mx Datasheet - Page 3

• Manufacturer Part Number: lm2637mx
• Description: Motherboard Power Supply Solution With A 5-bit Programmable Switching Controller And Two Linear Regulator Controllers
• Manufacturer: National Semiconductor Corporation

B
V
V
t
D
1.5V LDO CONTROLLER SECTION
V
R
I
V
V
2.5V LDO CONTROLLER SECTION
V
R
I
V
V
SS
SNS2
SNS3
WEA
RAMP_L
RAMP_H
SNS2
PWGD_HI
PWGD_LO
SNS3
PWGD_HI
PWGD_LO
Electrical Characteristics
STEP_SS
OUT2
OUT3
V
appearing in boldface type apply over the 0˚C to +70˚C range.
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
ambient thermal resistance, θ
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.
Symbol
CC
= 5V, V
Error Amplifier Unity Gain
Bandwidth
Ramp Signal Valley Voltage
Ramp Signal Peak Voltage
Soft Start Time
Duty Cycle Step Change in Soft
Start
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
DD
= 12V unless otherwise specified. Typicals and limits appearing in plain type apply for T
A
. The maximum allowable power dissipation at any ambient temperature is calculated using: P
JA
Parameter
, for LM2637 is 78˚C/W. For a T
(Continued)
V
5.25V, I
(Figure 1)
When Regulating
V
5.25V, I
(Figure 1)
When Regulating
DD
DD
JMAX
= 12V, V
= 12V, V
of 150˚C and T
G2
G3
Conditions
= 0 mA to 20 mA
= 0 mA to 20 mA
(Note 4)
(Note 4)
(Note 4)
(Note 4)
CC
CC
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, θ
1.463
2.438
Min
MAX
4096
1.25
3.25
12.5
0.63
0.44
0.63
0.44
Typ
200
200
1.5
2.5
= (T
21
21
5
JMAX
A
= T
− T
A
1.538
2.563
J
Max
)/θ
= +25˚C. Limits
JA
. The junction-to-
www.national.com
JA
, and the
Cycles
Units
Clock
MHz
µA
µA
%
V
V
V
Ω
V
V
V
Ω
V
V