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National Semiconductor Electronic Components Datasheet

LM3489Q Datasheet

Hysteretic PFET Buck Controller

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June 23, 2008
LM3489/LM3489Q
Hysteretic PFET Buck Controller with Enable Pin
General Description
The LM3489 is a high efficiency PFET switching regulator
controller that can be used to quickly and easily develop a
small, cost effective, switching buck regulator for a wide range
of applications. The hysteretic control architecture provides
for simple design without any control loop stability concerns
using a wide variety of external components. The PFET ar-
chitecture also allows for low component count as well as
ultra-low dropout, 100% duty cycle operation. Another benefit
is high efficiency operation at light loads without an increase
www.DinatoauSthpeuterti4pUp.lec.oAmdedicated Enable Pin provides a shutdown
mode drawing only 7µA. Leaving the Enable Pin unconnected
defaults to on.
Current limit protection can be implemented by measuring the
voltage across the PFET’s RDS(ON), thus eliminating the need
for a sense resistor. A sense resistor may be used to improve
current limit accuracy if desired. The cycle-by-cycle current
limit can be adjusted with a single resistor, ensuring safe op-
eration over a range of output currents.
Features
Easy to use control methodology
No control loop compensation required
Wide 4.5V to 35V input range
1.239V to VIN adjustable output range
High efficiency 93%
±1.3% (±2% over temp) internal reference
100% duty cycle operation
Maximum operation frequency > 1MHz
Current limit protection
Dedicated enable pin (on if unconnected)
Shutdown mode draws only 7µA supply current
MSOP-8
LM3489 is AEC-Q100 Grade 1 qualified
Applications
Set-Top Box
DSL/Cable Modem
PC/IA
Auto PC
TFT Monitor
Battery Powered Portable Applications
Distributed Power Systems
Always On Power
High Power LED Driver
Automotive
Typical Application Circuit
© 2008 National Semiconductor Corporation 201869
20186908
www.national.com


National Semiconductor Electronic Components Datasheet

LM3489Q Datasheet

Hysteretic PFET Buck Controller

No Preview Available !

Connection Diagram
Top View
20186909
8 Lead Plastic MSOP-8
NS package Number MUA08A
Package Marking and Ordering Information
Order Number
www.DataSheeLtM4U3.4c8o9mMM
LM3489MMX
LM3489QMM
LM3489QMMX
Package Type
MSOP-8
MSOP-8
MSOP-8
MSOP-8
Package Marking
SKSB
SKSB
STEB
STEB
Supplied As:
1000 units on Tape and Reel
3500 units on Tape and Reel
1000 units on Tape and Reel
3000 units on Tape and Reel
Automotive Grade*
No
No
Grade 1
Grade 1
*Automotive Grade (Q) product incorporates enhanced manufacturing and support processes for the automotive market, including defect detection methodologies.
Reliability qualification is compliant with the requirements and temperature grades defined in the AEC-Q100 standard. Automotive grade products are identified
with the letter Q. For more information go to http://www.national.com/automotive.
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
Name
ISENSE
GND
EN
FB
ADJ
PGND
PGATE
VIN
Description
The current sense input pin. This pin should be connected to the PFET drain terminal
directly or through a series resistor up to 600 ohm for 28V>Vin>35V.
Signal ground.
Enable pin. Connect EN pin to ground to shutdown the part or float to enable operation
(Internally pulled high). This pin can also be used to perform UVLO function.
The feedback input. Connect the FB to a resistor voltage divider between the output
and GND for an adjustable output voltage.
Current limit threshold adjustment. Connected to an internal 5.5µA current source. A
resistor is connected between this pin and VIN. The voltage across this resistor is
compared with the ISENSE pin voltage to determine if an over-current condition has
occurred.
Power ground.
Gate Drive output for the external PFET. PGATE swings between VIN and VIN-5V.
Power supply input pin.
www.national.com
2


Part Number LM3489Q
Description Hysteretic PFET Buck Controller
Maker National Semiconductor
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LM3489Q Datasheet PDF






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