Switching node connection to the internal PFET switch and NFET synchronous rectifier
Analog supply input. Connect to the input filter capacitor (Figure 1).
Power supply Input. Connect to the input filter capacitor (Figure 1).
Output voltage select ( For example)
VSELECT = LOW, V
OUT
= 0.8V
VSELECT = HIGH , V
OUT
= 1.2V
Power Good Flag. This commom drain logic output is pulled to ground when the output
voltage is not within +/-7.5% of regulation.
Connect PWM pin to VIN.
Enable pin. The device is in shutdown mode when voltage to this pin is <0.4V and enabled
when >1.0V. Do not leave this pin floating.
Feedback analog input. Connect directly to the output filter capacitor for fixed voltage
versions.
Die Attach Pad, connect the DAP to GND on PCB layout to enhance thermal
performance. It should not be used as a primary ground connection.
7
8
9
10
DAP
PGOOD
PWM
EN
FB
DAP
Ordering Information
Voltage Option
0.8V/1.2V
Order Number
LM3678SDE-1.2
LM3678SD-1.2
LM3678SDX-1.2
Package Marking
S021B
S021B
S021B
Supplied As
250 units, Tape-and-Reel
1000 units, Tape-and-Reel
4500 units, Tape-and-Reel
3
www.national.com
LM3678
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
Pin: Voltage to GND
EN Pin:
FB, SW Pin:
Continuous Power Dissipation
(Note 3)
Junction Temperature (T
J-MAX
)
−0.2V to 6.0V
−0.2V to 6.0V
(GND−0.2V) to
(V
IN
+ 0.2V)
Internally Limited
+150°C
Storage Temperature Range
Maximum Lead Temperature
(Soldering, 10 sec.)
−65°C to +150°C
260°C
Operating Ratings
(Notes 1, 2)
Input Voltage Range
2.5V to 5.5V
Recommended Load Current
0mA to 1.5A
Junction Temperature (T
J
) Range
−30°C to +125°C
Ambient Temperature (T
A
) Range (Note −30°C to +85°C
4)
Thermal Properties
Junction-to-Ambient Thermal
Resistance (θ
JA
) (LLP-10) for
4 layer board (Note 5)
49.8°C/W
Electrical Characteristics
Symbol
V
FB
V
REF
R
DSON (P)
R
DSON (N)
I
LIM
I
SHDN
EN
IH
EN
IL
I
EN
F
OSC
Parameter
Feedback Voltage
Internal Reference Voltage
Pin-Pin Resistance for PFET
Pin-Pin Resistance for NFET
Switch Peak Current Limit
Shutdown Supply Current
Logic High Input
Logic Low Input
Enable (EN) Input Current
Internal Oscillator Frequency
(Notes 2, 6, 8) Limits in standard typeface are for T
J
= 25°C. Limits in
boldface
type
apply over the full operating ambient temperature range (−30°C
≤
T
A
≤
+85°C). Unless otherwise noted, specifications apply to
the LM3678 Typical Application Circuit (pg. 1) with V
IN
= EN = 3.6V
Condition
VSELECT = Low & High
(Note 7)
V
IN
= V
GS
= 3.6V
V
IN
= V
GS
= 3.6V
Open loop
EN = 0V
V
IN
= 3.6V
V
IN
= 3.6V
0.01
PWM Mode
2.7
3.3
1.2
0.4
1
3.6
1.9
Min
-3
0.5
150
110
2.15
200
150
2.4
1
Typ
Max
+3
Units
%
V
mΩ
mΩ
A
µA
V
V
µA
MHz
Note 1:
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of
the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see
the Electrical Characteristics tables.
Note 2:
All voltages are with respect to the potential at the GND pin.
Note 3:
Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at T
J
= 150°C (typ.) and disengages at
T
J
= 130°C (typ.).
Note 4:
In Applications where high power dissipation and/or poor package resistance is present, the maximum ambient temperature may have to be derated.
Maximum ambient temperature (T
A-MAX
) is dependent on the maximum operating junction temperature (T
J-MAX
), the maximum power dissipation of the device in
the application (P
D-MAX
) and the junction to ambient thermal resistance of the package (θ
JA
) in the application, as given by the following equation: T
A-MAX
= T
J-MAX
− (θ
JA
x P
D-MAX
).
Note 5:
Junction to ambient thermal resistance is highly application and board layout dependent. In applications where high power dissipation exists, special care
must be given to thermal dissipation issues in board design.
Note 6:
Refer to datasheet curves for closed loop data and its variation with regards to supply voltage and temperature. Electrical Characteristic table reflects
open loop data (FB=0V and current drawn from SW pin ramped up until cycle by cycle current limit is activated). Closed loop current limit is the peak inductor
current measured in the application circuit by increasing output current until output voltage drops by 10%.
Note 7:
Min and Max limits are guaranteed by design, test or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm.
Note 8:
The parameters in the electrical characteristic table are tested at V
IN
= 3.6V unless otherwise specified. For performance over the input voltage range
