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PDF LM2642MTC Data sheet ( Hoja de datos )
| Número de pieza | LM2642MTC | |
| Descripción | Two-Phase Synchronous Step-Down Switching Controller | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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May 2003
LM2642
Two-Phase Synchronous Step-Down Switching
Controller
General Description
The LM2642 consists of two current mode synchronous
buck regulator controllers with a switching frequency of
300kHz.
The two switching regulator controllers operate 180˚ out of
phase. This feature reduces the input ripple RMS current,
thereby significantly reducing the required input capacitance.
The two switching regulator outputs can also be paralleled to
operate as a dual-phase single output regulator.
The output of each channel can be independently adjusted
from 1.3 to VIN• maximum duty cycle. An internal 5V rail is
also available externally for driving bootstrap circuitry.
Current-mode feedback control assures excellent line and
load regulation and a wide loop bandwidth for excellent
response to fast load transients. Current is sensed across
either the Vds of the top FET or across an external current-
sense resistor connected in series with the drain of the top
FET. Current limit is independently adjustable for each chan-
nel.
The LM2642 features analog soft-start circuitry that is inde-
pendent of the output load and output capacitance. This
makes the soft-start behavior more predictable and control-
lable than traditional soft-start circuits.
A PGOOD1 pin is provided to monitor the dc output of
channel 1. Over-voltage protection is available for both out-
puts. A UV-Delay pin is also available to allow delayed shut
off time for the IC during an output under-voltage event.
Features
n Two synchronous buck regulators
n 180˚ out of phase operation
n 4.5V to 30V input range
n Power good function monitors Ch.1
n 37µA Shutdown current
n 0.04% (typical) line and load regulation error
n Current mode control with or without a sense resistor
n Independent enable/soft-start pins allow simple
sequential startup configuration.
n Configurable for single output parallel operation. (See
Figure 2).
n Adjustable cycle-by-cycle current limit
n Input under-voltage lockout
n Output over-voltage latch protection
n Output under-voltage protection with delay
n Thermal shutdown
n Self discharge of output capacitors when the regulator is
OFF
n TSSOP package
Applications
n Embedded computer systems
n High end gaming systems
n Set-top boxes
n WebPAD
Block Diagram
© 2003 National Semiconductor Corporation DS200462
20046201
www.national.com
1 page  
Electrical Characteristics (Continued)
Unless otherwise specified, VIN = 15V, GND = PGND = 0V, VLIN5 = VDD1 = VDD2. Limits appearing in boldface type apply
over the specified operating junction temperature range, (-20˚C to +125˚C, if not otherwise specified). Specifications appearing
in plain type are measured using low duty cycle pulse testing with TA = 25˚C (Note 6), (Note 7). Min/Max limits are guaranteed
by design, test, or statistical analysis.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
Isk_uvdelay
VUVDelay
UV_DELAY Sink Current
UV_DELAY Threshold
Voltage
UV-DELAY = 0.4V
0.2 0.48 1.2
2.3
mA
V
VUVP
FB1, FB2, Under
Voltage Protection Latch
Threshold
As a percentage of nominal output
voltage (falling edge)
75 80 86
%
Hysteresis
4%
VOVP
VOUT Overvoltage
Shutdown Latch
Threshold
As a percentage measured at VFB1,
VFB2
107 113 122
%
Vpwrbad
Regulator Window
Detector Thresholds
(PGOOD1 from High to
Low)
As a percentage of output voltage
86.5
90.3
94.5
%
Vpwrgd
Regulator Window
Detector Thresholds
(PGOOD1 from Low to
High)
91.5 94 97.0
%
Swx_R
SW1, SW2
ON-Resistance
VSW1 = VSW2 = 2V
420 480 535
Ω
Gate Drive
ICBOOT
CBOOTx Leakage
Current
VCBOOT1 = VCBOOT2 = 7V
10 nA
ISC_DRV
HDRVx and LDRVx
Source Current
VCBOOT1 = VCBOOT2 = 5V, VSWx=0V,
HDRVx=LDRVx=2.5V
0.5
A
Isk_HDRV
HDRVx Sink Current
VCBOOTx = VDDx = 5V, VSWx = 0V,
0.8
A
HDRVX = 2.5V
Isk_LDRV
LDRVx Sink Current
VCBOOTx = VDDx = 5V, VSWx = 0V,
1.1
A
LDRVX = 2.5V
RHDRV
HDRV1 & 2 Source
On-Resistance
HDRV1 & 2 Sink
On-Resistance
VCBOOT1 = VCBOOT2 = 5V,
VSW1 = VSW2 = 0V
3.1 Ω
1.5 Ω
RLDRV
LDRV1 & 2 Source
On-Resistance
LDRV1 & 2 Sink
On-Resistance
VCBOOT1 = VCBOOT2 = 5V,
VSW1 = VSW2 = 0V
VDD1 = VDD1 = 5V
3.1 Ω
1.1 Ω
Oscillator
Fosc Oscillator Frequency
-40˚C to 125˚C
260 300 340
kHz
257.5
340
Don_max
Maximum On-Duty Cycle
VFB1 = VFB2 = 1V, Measured at pins
HDRV1 and HDRV2
-40˚C to 125˚C
96
95.64
98
%
Ton_min
SSOT_delta
Minimum On-Time
HDRV1 and HDRV2
Delta On Time
ON/SS1 = ON/SS2 = 2V
166
20 150
ns
ns
Error Amplifier
5 www.national.com
5 Page 
Typical Performance Characteristics (Continued)
Ch.2 Load Transient Response
3.3VOUT, 12VIN
Load Transient Response
Parallel Operation 1.8VOUT, 12VIN
20046229
Input Supply Current vs Temperature
(Shutdown Mode VIN = 15V)
20046228
Input Supply Current vs VIN
Shutdown Mode (25˚C)
VLIN5 vs Temperature
20046224
VLIN5 vs VIN (25˚C)
20046225
20046226
11
20046227
www.national.com
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LM2642MTC.PDF ] | |
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