LM2647LQ Datasheet PDF - National Semiconductor
| Part Number | LM2647LQ | |
| Description | Dual Synchronous Buck Regulator Controller | |
| Manufacturers | National Semiconductor | |
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June 2003
LM2647
Dual Synchronous Buck Regulator Controller
General Description
The LM2647 is an adjustable 200-500kHz dual channel
voltage-mode controlled high-speed synchronous buck
regulator controller ideally suited for battery powered appli-
cations such as laptop and notebook computers. The
LM2647 requires only N-channel FETs for both the upper
and lower positions of each synchronous stage. It features
line feedforward to improve the response to input transients.
At very light loads, the user can choose between the high-
efficiency Pulse-skip mode or the constant frequency
Forced-PWM mode. Lossless current limiting without the use
of external sense resistors is made possible by sensing the
voltage drop across the bottom FET. A unique adaptive duty
cycle clamping technique is incorporated to significantly re-
duce peak currents under abnormal load conditions. The two
independently programmable outputs switch 180˚ out of
phase (interleaved switching) to reduce the input capacitor
and filter requirements. The input voltage range is 5.5V to
28V while the output voltages are adjustable down to 0.6V.
Standard supervisory and control features include Soft-start,
Power Good, output Under-voltage and Over-voltage protec-
tion, Under-voltage Lockout, Soft-shutdown and Enable.
Features
n Input voltage range from 5.5V to 28V
n Synchronous dual-channel Interleaved switching
n Forced-PWM or Pulse-skip modes
n Lossless bottom-side FET current sensing
n Adaptive duty cycle clamping
n High current N-channel FET drivers
n Low shutdown supply currents
n Reference voltage accurate to within ±1.5%
n Output voltage adjustable down to 0.6V
n Power Good flag and Chip Enable
n Under-voltage lockout
n Over-voltage/Under-voltage protection
n Soft-start and Soft-shutdown
n Switching frequency adjustable 200kHz-500kHz
Applications
n Notebook Chipset Power Supplies
n Low Output Voltage High-Efficiency Buck Regulators
Typical Application (Channel 2 in parenthesis)
© 2003 National Semiconductor Corporation DS200563
20056304
www.national.com
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Voltages from the indicated pins to SGND/PGND unless
otherwise indicated (Note 2):
VIN 30V
V5 7V
VDD
7V
BOOT1, BOOT2
36V
BOOT1 to SW1, BOOT2 to
SW2
7V
SW1, SW2
30V
ILIM1, ILIM2
30V
SENSE1, SENSE2, FB1, FB2
7V
PGOOD
7V
EN 7V
Power Dissipation (TA = 25˚C)
(Note 3)
Junction Temperature
ESD Rating (Note 4)
Ambient Storage Temperature
Range
Soldering Dwell Time,
Temperature
Wave
Infrared
Vapor Phase
1.0W
+150˚C
2kV
-65˚C to +150˚C
4 sec, 260˚C
10 sec, 240˚C
75 sec, 219˚C
Operating Ratings (Note 1)
VIN
VDD, V5
Junction Temperature
5.5V to 28V
4.5V to 5.5V
-5˚C to +125˚C
Electrical Characteristics
Specifications with standard typeface are for TJ = 25˚C, and those with boldface apply over full Operating Junction Tempera-
ture range. VDD = V5 = 5V, VSGND = VPGND = 0V, VIN = 15V, VEN = 3V, RFADJ = 22.1K unless otherwise stated. (Note 5)
Symbol
Parameter
Conditions
Min Typical Max
(Note 6) (Note 7) (Note 6)
Units
Reference
VFB_REG
FB Pin Voltage at Regualtion VDD = 4.5V to 5.5V,
(either FB Pin)
VIN = 5.5V to 28V
591 600 609 mV
VFB Line Regulation
VDD = 4.5V to 5.5V,
VIN = 5.5V to 28V
0.5
IFB FB Pin Current (sourcing)
Chip Supply
VFB at regulation
20 100 nA
IQ_VIN
ISD_VN
IQ_VDD
ISD_VDD
IQ_V5
ISD_V5
IQ_BOOT
ISD_BOOT
VUVLO
Logic
VIN Quiescent Current
VIN Shutdown Current
VDD Quiescent Current
VDD Shutdown Current
V5 Normal Operating Current
V5 Shutdown Current
BOOT Quiescent Current
BOOT Shutdown Current
VDD UVLO Threshold
VDD UVLO Hysteresis
VFB1 = VFB2 = 0.7V
VEN = 0V
VFB1 = VFB2 = 0.7V
VEN = 0V
VFB1 = VFB2 = 0.7V
VFB1 = VFB2 = 0.5V
VEN = 0V
VFB1 = VFB2 = 0.7V
VFB1 = VFB2 = 0.5V
VEN = 0V
VDD rising from 0V
VDD = V5 falling from VUVLO
100 200
µA
0 5 µA
2.5 4 mA
8 15 µA
0.3 0.5 mA
1 1.5
0 5 µA
2 5 µA
300 500
1 5 µA
3.9 4.2 4.5
V
0.5 0.7 0.9
V
IEN
VEN_HI
VEN_LO
VFPWM_HI
VFPWM_LO
EN Input Current
EN Input Logic High
EN Input Logic Low
FPWM Pull-down
FPWM Input Logic High
FPWM Input Logic Low
VEN = 0 to 5V
VFPWM = 2V
0 µA
2 1.8
V
1.3 0.8
V
100 200 1000 kΩ
2 1.8
V
1.3 0.8
V
5 www.national.com
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| Information | Total 25 Pages | |
| Link URL | [ Copy URL to Clipboard ] | |
| Download | [ LM2647LQ.PDF Datasheet ] | |
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