Connect the ground of the feedback network to an AGND
plane which should be tied directly to the GND pin.
SHDN(Pin 4):
Shutdown Pin. The shutdown pin is an active
low control. Tie this pin above 1.1V to enable the device. Tie
this pin below 0.3V to turn off the device.
V
IN
(Pin 5):
Input Supply Pin. Bypass this pin with a capacitor
as close to the device as possible.
Function
SW(Pin 1):
Switch Pin. This is the drain of the internal
NMOS power switch. Minimize the metal trace area con-
nected to this pin to minimize EMI.
GND(Pin 2):
Ground Pin. Tie directly to ground plane.
FB(Pin 3):
Feedback Pin. Set the output voltage by selecting
values for R1 and R2 using:
www.national.com
2
LM2704
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
IN
SW Voltage
FB Voltage
SHDN Voltage
Maximum Junction Temp. T
J
(Note 2)
Lead Temperature
(Soldering 10 sec.)
Vapor Phase
(60 sec.)
7.5V
21V
2V
7.5V
150˚C
Infrared
(15 sec.)
ESD Ratings (Note 3)
Human Body Model
Machine Model (Note 4)
220˚C
2kV
200V
Operating Conditions
Junction Temperature
(Note 5)
Supply Voltage
SW Voltage Max.
−40˚C to +125˚C
2.2V to 7V
20.5V
300˚C
215˚C
Electrical Characteristics
(Note 5)
Specifications in standard type face are for T
J
= 25˚C and those in
boldface type
apply over the full
Operating Temperature
Range
(T
J
= −40˚C to +125˚C). Unless otherwise specified. V
IN
=2.2V.
Symbol
I
Q
Parameter
Device Disabled
Device Enabled
Shutdown
V
FB
I
CL
I
B
V
IN
R
DSON
T
OFF
I
SD
Feedback Trip Point
Switch Current Limit
FB Pin Bias Current
Input Voltage Range
Switch R
DSON
Switch Off Time
SHDN Pin Current
SHDN = V
IN
, T
J
= 25˚C
SHDN = V
IN
, T
J
= 125˚C
SHDN = GND
I
L
UVP
V
FB
Hysteresis
SHDN
Threshold
θ
JA
Switch Leakage Current
Input Undervoltage Lockout
Feedback Hysteresis
SHDN low
SHDN High
Thermal Resistance
1.1
V
SW
= 20V
ON/OFF Threshold
FB = 1.23V (Note 7)
2.2
0.7
400
0
15
0
0.05
1.8
8
0.7
0.7
220
0.3
5
µA
V
mV
V
˚C/W
80
nA
Conditions
FB = 1.3V
FB = 1.2V
SHDN = 0V
1.189
490
420
Min
(Note 5)
Typ
(Note 6)
40
235
0.01
1.237
550
30
Max
(Note 5)
70
300
2.5
1.269
610
620
120
7.0
1.6
V
mA
nA
V
Ω
ns
µA
Units
Note 1:
Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended to
be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2:
The maximum allowable power dissipation is a function of the maximum junction temperature, T
J
(MAX), the junction-to-ambient thermal resistance,
θ
JA
,
and the ambient temperature, T
A
. See the Electrical Characteristics table for the thermal resistance. The maximum allowable power dissipation at any ambient
temperature is calculated using: P
D
(MAX) = (T
J(MAX)
− T
A
)/θ
JA
. Exceeding the maximum allowable power dissipation will cause excessive die temperature.
Note 3:
The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged
directly into each pin.
Note 4:
ESD susceptibility using the machine model is 150V for SW pin.
Note 5:
All limits guaranteed at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are 100%
production tested or guaranteed through statistical analysis. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality
Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Note 6:
Typical numbers are at 25˚C and represent the most likely norm.
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