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PDF LM2832 Data sheet ( Hoja de datos )
| Número de pieza | LM2832 | |
| Descripción | High Frequency 2.0A Load - Step-Down DC-DC Regulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LM2832 (archivo pdf) en la parte inferior de esta página. Total 27 Páginas | ||
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www.DataSheet4U.com
August 2006
LM2832
High Frequency 2.0A Load - Step-Down DC-DC
Regulator
General Description
The LM2832 regulator is a monolithic, high frequency, PWM
step-down DC/DC converter in a 6 Pin LLP and a 8 Pin
eMSOP package. It provides all the active functions to pro-
vide local DC/DC conversion with fast transient response
and accurate regulation in the smallest possible PCB area.
With a minimum of external components, the LM2832 is
easy to use. The ability to drive 2.0A loads with an internal
150 mΩ PMOS switch using state-of-the-art 0.5 µm BiCMOS
technology results in the best power density available. The
world-class control circuitry allows on-times as low as 30ns,
thus supporting exceptionally high frequency conversion
over the entire 3V to 5.5V input operating range down to the
minimum output voltage of 0.6V. Switching frequency is
internally set to 550 kHz, 1.6 MHz, or 3.0 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 shut-
down is included, featuring an ultra-low stand-by current of
30 nA. The LM2832 utilizes current-mode control and inter-
nal compensation to provide high-performance regulation
over a wide range of operating conditions. Additional fea-
tures include internal soft-start circuitry to reduce inrush
current, pulse-by-pulse current limit, thermal shutdown, and
output over-voltage protection.
Features
n Input voltage range of 3.0V to 5.5V
n Output voltage range of 0.6V to 4.5V
n 2.0A output current
n High Switching Frequencies
1.6MHz (LM2832X)
0.55MHz (LM2832Y)
3.0MHz (LM2832Z)
n 150mΩ PMOS switch
n 0.6V, 2% Internal Voltage Reference
n Internal soft-start
n Current mode, PWM operation
n Thermal Shutdown
n Over voltage protection
Applications
n Local 5V to Vcore Step-Down Converters
n Core Power in HDDs
n Set-Top Boxes
n USB Powered Devices
n DSL Modems
Typical Application Circuit
20197564
20197581
© 2006 National Semiconductor Corporation DS201975
www.national.com
1 page  
Electrical Characteristics 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. (Continued)
Symbol
θJA
θJC
TSD
Parameter
Junction to Ambient
0 LFPM Air Flow (Note 3)
Junction to Case (Note 3)
Thermal Shutdown Temperature
Conditions
LLP-6 and eMSOP-8
Packages
LLP-6 and eMSOP-8
Packages
Min Typ Max Units
80
˚C/W
18
˚C/W
165 ˚C
Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Range indicates conditions for which the device is
intended to be functional, but does not guarantee specfic performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: Thermal shutdown will occur if the junction temperature exceeds the maximum junction temperature of the device.
Note 3: Applies for packages soldered directly onto a 3” x 3” PC board with 2oz. copper on 4 layers in still air.
5 www.national.com
5 Page 
Applications Information
THEORY OF OPERATION
The LM2832 is a constant frequency PWM buck regulator IC
that delivers a 2.0A load current. The regulator has a preset
switching frequency of 1.6MHz or 3.0MHz. This high fre-
quency allows the LM2832 to operate with small surface
mount capacitors and inductors, resulting in a DC/DC con-
verter that requires a minimum amount of board space. The
LM2832 is internally compensated, so it is simple to use and
requires few external components. The LM2832 uses
current-mode control to regulate the output voltage. The
following operating description of the LM2832 will refer to the
Simplified Block Diagram (Figure 1) and to the waveforms in
Figure 2. The LM2832 supplies a regulated output voltage by
switching the internal PMOS control switch at constant fre-
quency and variable duty cycle. A switching cycle begins at
the falling edge of the reset pulse generated by the internal
oscillator. When this pulse goes low, the output control logic
turns on the internal PMOS control switch. During this on-
time, the SW pin voltage (VSW) swings up to approximately
VIN, and the inductor current (IL) increases with a linear
slope. IL is measured by the current sense amplifier, which
generates an output proportional to the switch current. The
sense signal is summed with the regulator’s corrective ramp
and compared to the error amplifier’s output, which is pro-
portional to the difference between the feedback voltage and
VREF. When the PWM comparator output goes high, the
output switch turns off until the next switching cycle begins.
During the switch off-time, inductor current discharges
through the Schottky catch diode, which forces the SW pin to
swing below ground by the forward voltage (VD) of the
Schottky catch diode. The regulator loop adjusts the duty
cycle (D) to maintain a constant output voltage.
SOFT-START
This function forces VOUT to increase at a controlled rate
during start up. During soft-start, the error amplifier’s refer-
ence voltage ramps from 0V to its nominal value of 0.6V in
approximately 600 µs. This forces the regulator output to
ramp up in a controlled fashion, which helps reduce inrush
current.
OUTPUT OVERVOLTAGE PROTECTION
The over-voltage comparator compares the FB pin voltage
to a voltage that is 15% higher than the internal reference
VREF. Once the FB pin voltage goes 15% above the internal
reference, the internal PMOS control switch is turned off,
which allows the output voltage to decrease toward regula-
tion.
UNDERVOLTAGE LOCKOUT
Under-voltage lockout (UVLO) prevents the LM2832 from
operating until the input voltage exceeds 2.73V (typ). The
UVLO threshold has approximately 430 mV of hysteresis, so
the part will operate until VIN drops below 2.3V (typ). Hys-
teresis prevents the part from turning off during power up if
VIN is non-monotonic.
CURRENT LIMIT
The LM2832 uses cycle-by-cycle current limiting to protect
the output switch. During each switching cycle, a current limit
comparator detects if the output switch current exceeds
3.25A (typ), and turns off the switch until the next switching
cycle begins.
THERMAL SHUTDOWN
Thermal shutdown limits total power dissipation by turning
off the output switch when the IC junction temperature ex-
ceeds 165˚C. After thermal shutdown occurs, the output
switch doesn’t turn on until the junction temperature drops to
approximately 150˚C.
FIGURE 2. Typical Waveforms
20197566
11
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| Páginas | Total 27 Páginas | |
| PDF Descargar | [ Datasheet LM2832.PDF ] | |
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