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National Semiconductor Corporation
National Semiconductor Corporation

LM26420 Datasheet

High Frequency 2.0A Load - Step-Down DC-DC Regulator


LM26420 Datasheet Preview


LM26420
March 24, 2009
Dual 2.0A, High Frequency Synchronous Step-Down DC-
DC Regulator
www.daGtasehneeet4ru.acolmDescription
The LM26420 regulator is a monolithic, high frequency, dual
PWM step-down DC/DC converter in a 16 Pin LLP and a 20
Pin eTSSOP package. It provides all the active functions to
provide local DC/DC conversion with fast transient response
and accurate regulation in the smallest possible PCB area.
With a minimum of external components, the LM26420 is
easy to use. The ability to drive two 2.0A loads with an internal
75 mPMOS top switch and an internal 50 mNMOS bottom
switch using state-of-the-art 0.5 µm BiCMOS technology re-
sults in the best power density available. The world-class
control circuitry allows on-times as low as 30ns, thus sup-
porting exceptionally high frequency conversion over the en-
tire 3V to 5.5V input operating range down to the minimum
output voltage of 0.8V. Switching frequency is internally set
to 550 kHz or 2.2 MHz, allowing the use of extremely small
surface mount inductors and chip capacitors. Even though the
operating frequency is high, efficiencies up to 93% are easy
to achieve. External shutdown is included, featuring an ultra-
low stand-by current. The LM26420 utilizes current-mode
control and internal compensation to provide high-perfor-
mance regulation over a wide range of operating conditions.
Additional features include internal soft-start circuitry to re-
duce inrush current, pulse-by-pulse current limit, thermal
shutdown, power good indicators, precision enables, and out-
put over-voltage protection.
Features
Input voltage range of 3.0V to 5.5V
Output voltage range of 0.8V to 4.5V
2.0A output current per output
High Switching Frequencies
2.2MHz (LM26420X)
0.55MHz (LM26420Y)
75mPMOS switch
50mNMOS switch
0.8V, 1.5% Internal Voltage Reference
Internal soft-start
Independent power good for each output
Independent precision enable for each output
Current mode, PWM operation
Thermal Shutdown
Over voltage protection
Start-up into Pre-biased Output Loads
Outputs are 180° out of phase
Applications
Local 5V to Vcore Step-Down Converters
Core Power in HDDs
Set-Top Boxes
USB Powered Devices
DSL Modems
Powering Core and I/O voltages for FPGAs, CPLDs, and
ASICs
Typical Application Circuit
30069664
© 2009 National Semiconductor Corporation 300696
30069684
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Page 1

Connection Diagrams
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30069601
16-Pin LLP (TOP VIEW)
Ordering Information
Order Number
LM26420XMH
LM26420XMHX
LM26420XSQ
LM26420XSQX
LM26420YMH
LM26420YMHX
LM26420YSQ
LM26420YSQX
Frequency
Option
2.2MHz
0.55MHz
NOPB versions available as well
Package Type
eTSSOP-20
LLP-16
eTSSOP-20
LLP-16
30069602
20-Pin eTSSOP (TOP VIEW)
NSC Package
Drawing
MXA20A
SQB16A
MXA20A
SQB16A
Top Mark
LM26420XMH
L26420X
LM26420YMH
L26420Y
Supplied As
1000 units Tape and Reel
3500 units Tape and Reel
1000 units Tape and Reel
4500 units Tape and Reel
1000 units Tape and Reel
3500 units Tape and Reel
1000 units Tape and Reel
4500 units Tape and Reel
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2
Page 2

Pin Descriptions 20-Pin eTSSOP
Pin Name
3, 4
17, 18
1
VIND1
VIND2
VINC
6,7
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20
PGND1
PGND2
AGND
9
12
8
13
5
16
2
19
10, 11, DAP
PG1
PG2
FB1
FB2
SW1
SW2
EN1
EN2
Die Attach Pad
Function
Power Input supply for Buck 1.
Power Input supply for Buck 2.
Input supply for control circuitry.
Power ground pin for Buck 1.
Power ground pin for Buck 2.
Signal ground pin. Place the bottom resistor of the feedback network as close as possible
to pin.
Power Good Indicator for Buck 1. Pin is connected through a resistor to an external supply
(open drain output).
Power Good Indicator for Buck 2. Pin is connected through a resistor to an external supply
(open drain output).
Feedback pin for Buck 1. Connect to external resistor divider to set output voltage.
Feedback pin for Buck 2. Connect to external resistor divider to set output voltage.
Output switch for Buck 1. Connect to the inductor.
Output switch for Buck 2. Connect to the inductor.
Enable control input. Logic high enable operation for Buck 1. Do not allow this pin to float
or be greater than VIN + 0.3V.
Enable control input. Logic high enable operation for Buck 2. Do not allow this pin to float
or be greater than VIN + 0.3V.
Connect to system ground for low thermal impedance, but it cannot be used as a primary
GND connection.
Pin Descriptions 16-Pin LLP
Pin
1,2
11, 12
15
4
9
14
6
7
5
8
3
10
16
13
DAP
Name
VIND1
VIND2
VINC
PGND1
PGND2
AGND
PG1
PG2
FB1
FB2
SW1
SW2
EN1
EN2
Die Attach Pad
Function
Power Input supply for Buck 1.
Power Input supply for Buck 2.
Input supply for control circuitry.
Power ground pin for Buck 1.
Power ground pin for Buck 2.
Signal ground pin. Place the bottom resistor of the feedback network as close as possible
to pin.
Power Good Indicator for Buck 1. Pin is connected through a resistor to an external supply
(open drain output).
Power Good Indicator for Buck 2. Pin is connected through a resistor to an external supply
(open drain output).
Feedback pin for Buck 1. Connect to external resistor divider to set output voltage.
Feedback pin for Buck 2. Connect to external resistor divider to set output voltage.
Output switch for Buck 1. Connect to the inductor.
Output switch for Buck 2. Connect to the inductor.
Enable control input. Logic high enable operation for Buck 1. Do not allow this pin to float
or be greater than VIN + 0.3V.
Enable control input. Logic high enable operation for Buck 2. Do not allow this pin to float
or be greater than VIN + 0.3V.
Connect to system ground for low thermal impedance and as a primary electrical GND
connection.
3 www.national.com
Page 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.
VIN
FB Voltage
EN Voltage
www.datasheSeWt4uV.cooltmage
ESD Susceptibility
Human Body Model (Note 3)
-0.5V to 7V
-0.5V to 3V
-0.5V to 7V
-0.5V to 7V
1.5kV
Junction Temperature (Note 2)
Storage Temperature
Soldering Information
Infrared or Convection Reflow
(15 sec)
Operating Ratings
VIN
Junction Temperature
150°C
−65°C to +150°C
220°C
3V to 5.5V
−40°C to +125°C
Electrical Characteristics Per Buck VIN = 5V unless otherwise indicated under the Conditions column.
Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C to
+125°C. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the
most likely parametric norm at TJ = 25°C, and are provided for reference purposes only.
Symbol
Parameter
Conditions
Min Typ Max Units
VFB
ΔVFB/VIN
IB
UVLO
Feedback Voltage
Feedback Voltage Line Regulation
Feedback Input Bias Current
Under-voltage Lockout
UVLO Hysteresis
VIN = 3V to 5.5V
VIN Rising
VIN Falling
0.788
2.0
0.800
0.05
0.40
2.628
2.3
330
0.812
100
2.90
V
%/V
nA
V
V
mV
FSW Switching Frequency
LM26420-X
LM26420-Y
1.85 2.2 2.65
MHz
0.4 0.55 0.7
FFB Frequency Fold-back
LM26420-X
LM26420-Y
300
kHz
150
DMAX
Maximum Duty Cycle
LM26420-X
LM26420-Y
86 91.5
90 98
%
RDSON_TOP TOP Switch On Resistance
LLP-16 Package
eTSSOP-20 Package
75 135
70 135 m
RDSON_BOT BOTTOM Switch On Resistance
LLP-16 Package
eTSSOP-20 Package
55 100
45 80 m
ICL_TOP
ICL_BOT
ΔΦ
TOP Switch Current Limit
BOTTOM Switch Reverse Current Limit
Phase Shift Between SW1 and SW2
VIN = 3.3V
VIN = 3.3V
2.4 3.3
0.4 0.75
160 180 200
A
A
°
VEN_TH
Enable Threshold Voltage
Enable Threshold Hysteresis
0.97 1.04 1.12
0.15
V
ISW_TOP
IEN
VPG-TH-U
Switch Leakage
Enable Pin Current
Upper Power Good Threshold
Upper Power Good Hysteresis
Sink/Source
FB Pin Voltage Rising
-0.7 µA
5.0 nA
848 925 1,008 mV
40 mV
VPG-TH-L
Lower Power Good Threshold
Lower Power Good Hysteresis
FB Pin Voltage Rising
656 710 791 mV
40 mV
IQVINC
VINC Quiescent Current (non-switching)
with both outputs on
VINC Quiescent Current (switching) with
both outputs on
LM26420X/Y VFB = 0.9
LM26420X/Y VFB = 0.7
3.3 5.0
mA
4.7 6.2
IQVIND
VINC Quiescent Current (shutdown)
VIND Quiescent Current (non-switching)
VIND Quiescent Current (switching)
VIND Quiescent Current (shutdown)
All Options VEN = 0V
LM26420X/Y VFB = 0.9
LM26420X VFB = 0.7
LM26420Y VFB = 0.7
All Options VEN = 0V
0.05
0.9 1.5
11.0 15.0
3.7 7.5
0.1
µA
mA
µA
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4
Page 4
Part Number LM26420
Manufactur National Semiconductor Corporation
Description High Frequency 2.0A Load - Step-Down DC-DC Regulator
Total Page 28 Pages
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