LM2622
600kHz/1.3MHz Step-up PWM DC/DC Converter
General Description
The LM2622 is a step-up DC/DC converter with a 1.6A, 0.2
internal switch and pin selectable operating frequency. With
the ability to convert 3.3V to multiple outputs of 8V, -8V, and
23V, the LM2622 is an ideal part for biasing TFT displays.
The LM2622 can be operated at switching frequencies of
600kHz and 1.3MHz allowing for easy filtering and low noise.
An external compensation pin gives the user flexibility in
setting frequency compensation, which makes possible the
use of small, low ESR ceramic capacitors at the output. The
LM2622 is available in a low profile 8-lead MSOP package.
Features
n
1.6A, 0.2
, internal switch
n
Operating voltage as low as 2.0V
n
600kHz/1.3MHz pin selectable frequency operation
n
Over temperature protection
n
8-Lead MSOP package
Applications
n
TFT Bias Supplies
n
Handheld Devices
n
Portable Applications
n
GSM/CDMA Phones
n
Digital Cameras
Typical Application Circuit
10127331
600 kHz Operation
October 2001
LM2622
600kHz/1.3MHz
Step-up
PWM
DC/DC
Converter
2001 National Semiconductor Corporation
DS101273
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Connection Diagram
Top View
10127304
8-Lead Plastic MSOP
NS Package Number MUA08A
Ordering Information
Order Number
Package Type
NSC Package
Drawing
Supplied As
Package ID
LM2622MM-ADJ
MSOP-8
MUA08A
1000 Units, Tape and
Reel
S18B
LM2622MMX-ADJ
MSOP-8
MUA08A
3500 Units, Tape and
Reel
S18B
Pin Description
Pin
Name
Function
1
V
C
Compensation network connection. Connected to the output of the voltage error amplifier.
2
FB
Output voltage feedback input.
3
SHDN
Shutdown control input, active low.
4
GND
Analog and power ground.
5
SW
Power switch input. Switch connected between SW pin and GND pin.
6
V
IN
Analog power input.
7
FSLCT
Switching frequency select input. V
IN
= 1.3MHz. Ground = 600kHz.
8
NC
Connect to ground.
LM2622
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2
Block Diagram
10127303
LM2622
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3
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
12V
SW Voltage
18V
FB Voltage
7V
V
C
Voltage
7V
SHDN Voltage
7V
FSLCT
12V
Maximum Junction
Temperature
150C
Power Dissipation(Note 2)
Internally Limited
Lead Temperature
300C
Vapor Phase (60 sec.)
215C
Infrared (15 sec.)
220C
ESD Susceptibility
(Note 3)
Human Body Model
2kV
Machine Model
200V
Operating Conditions
Operating Junction
Temperature Range (Note 4)
-40C to +125C
Storage Temperature
-65C to +150C
Supply Voltage
2V to 12V
Electrical Characteristics
Specifications in standard type face are for T
J
= 25C and those with boldface type apply over the full Operating Tempera-
ture Range ( T
J
= -40C to +125C)Unless otherwise specified. V
IN
=2.0V and I
L
= 0A, unless otherwise specified.
Symbol
Parameter
Conditions
Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Units
I
Q
Quiescent Current
FB = 0V (Not Switching)
1.3
2.0
mA
V
SHDN
= 0V
5
10
A
V
FB
Feedback Voltage
1.2285
1.26
1.2915
V
I
CL
(Note 6)
Switch Current Limit
V
IN
= 2.7V (Note 7)
1.0
1.65
2.3
A
V
O
/
I
LOAD
Load Regulation
V
IN
= 3.3V
6.7
mV/A
%V
FB
/
V
IN
Feedback Voltage Line
Regulation
2.0V
V
IN
12.0V
0.013
0.1
%/V
I
B
FB Pin Bias Current (Note 8)
0.5
20
nA
V
IN
Input Voltage Range
2
12
V
g
m
Error Amp Transconductance
I = 5A
40
135
290
mho
A
V
Error Amp Voltage Gain
135
V/V
D
MAX
Maximum Duty Cycle
78
85
%
f
S
Switching Frequency
FSLCT = Ground
480
600
720
kHz
FSLCT = V
IN
1
1.25
1.5
MHz
I
SHDN
Shutdown Pin Current
V
SHDN
= V
IN
0.01
0.1
A
V
SHDN
= 0V
-0.5
-1
I
L
Switch Leakage Current
V
SW
= 18V
0.01
3
A
R
DSON
Switch R
DSON
V
IN
= 2.7V, I
SW
= 1A
0.2
0.4
Th
SHDN
SHDN Threshold
Output High
0.9
0.6
V
Output Low
0.6
0.3
V
UVP
On Threshold
1.8
1.92
2.0
V
Off Threshold
1.7
1.82
1.9
V
JA
Thermal Resistance
Junction to Ambient(Note 9)
235
C/W
Junction to Ambient(Note 10)
225
Junction to Ambient(Note 11)
220
Junction to Ambient(Note 12)
200
Junction to Ambient(Note 13)
195
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,
JA
,
and the ambient temperature, T
A
. See the Electrical Characteristics table for the thermal resistance of various layouts. The maximum allowable power dissipation
at any ambient temperature is calculated using: P
D
(MAX) = (T
J(MAX)
- T
A
)/
JA
. Exceeding the maximum allowable power dissipation will cause excessive die
temperature, and the regulator will go into thermal shutdown.
LM2622
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4
Electrical Characteristics
(Continued)
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5k
resistor into each pin. The machine model is a 200pF capacitor discharged
directly into each pin.
Note 4: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are 100%
production tested. 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 5: Typical numbers are at 25C and represent the most likely norm.
Note 6: Duty cycle affects current limit due to ramp generator.
Note 7: Current limit at 0% duty cycle. See TYPICAL PERFORMANCE section for Switch Current Limit vs. V
IN
Note 8: Bias current flows into FB pin.
Note 9: Junction to ambient thermal resistance (no external heat sink) for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit.
See 'Scenario 'A'' in the Power Dissipation section.
Note 10: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.0191 sq. in. of copper heat sinking. See 'Scenario 'B'' in the Power Dissipation section.
Note 11: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.0465 sq. in. of copper heat sinking. See 'Scenario 'C'' in the Power Dissipation section.
Note 12: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.2523 sq. in. of copper heat sinking. See 'Scenario 'D'' in the Power Dissipation section.
Note 13: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.0098 sq. in. of copper heat sinking on the top layer and 0.0760 sq. in. of copper heat sinking on the bottom layer, with three 0.020 in. vias connecting the planes.
See 'Scenario 'E'' in the Power Dissipation section.
Typical Performance Characteristics
Efficiency vs. Load Current
(V
OUT
= 8V, f
S
= 600 kHz)
Efficiency vs. Load Current
(V
OUT
= 8V, f
S
= 1.3 MHz)
10127326
10127325
Switch Current Limit vs. Temperature
(V
IN
= 3.3V, V
OUT
= 8V)
Switch Current Limit vs. V
IN
10127320
10127322
LM2622
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