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PDF LM21215A-1 Data sheet ( Hoja de datos )
| Número de pieza | LM21215A-1 | |
| Descripción | 15A High Efficiency Synchronous Buck Regulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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LM21215A-1
March 27, 2011
15A High Efficiency Synchronous Buck Regulator with
Frequency Synchronization
General Description
The LM21215A-1 is a monolithic synchronous buck regulator
that is capable of delivering up to 15A of continuous output
current while producing an output voltage down to 0.6V with
outstanding efficiency. The device is optimized to work over
an input voltage range of 2.95V to 5.5V, making it suited for
a wide variety of low voltage systems. The voltage mode con-
trol loop provides high noise immunity, narrow duty cycle
capability and can be compensated to be stable with any type
of output capacitance, providing maximum flexibility and ease
of use.
The LM21215A-1 features internal over voltage protection
(OVP) and over-current protection (OCP) for increased sys-
tem reliability. A precision enable pin and integrated UVLO
allow turn-on of the device to be tightly controlled and se-
quenced. Startup inrush currents are limited by both an inter-
nally fixed and externally adjustable soft-start circuit. Fault
detection and supply sequencing are possible with the inte-
grated power good circuit.
The LM21215A-1 is designed to work well in multi-rail power
supply architectures. The output voltage of the device can be
configured to track an external voltage rail using the SS/TRK
pin. The switching frequency can be synchronized to the
falling edge of a clock between frequencies of 300kHz to
1.5MHz.
If the output is pre-biased at startup, it will not sink current,
allowing the output to smoothly rise past the pre-biased volt-
age. The regulator is offered in a 20-pin eTSSOP package
with an exposed pad that can be soldered to the PCB, elimi-
nating the need for bulky heatsinks.
Features
■ Integrated 7.0 mΩ high side and 4.3 mΩ low side FET
switches
■ 300 kHz to 1.5 MHz frequency SYNC pin
■ Adjustable output voltage from 0.6V to VIN (100% duty
cycle capable), ±1% reference
■ Input voltage range 2.95V to 5.5V
■ Startup into pre-biased loads
■ Output voltage tracking capability
■ Wide bandwidth voltage loop error amplifier
■ Adjustable soft-start with external capacitor
■ Precision enable pin with hysteresis
■ Integrated OVP, OCP, OTP, UVLO and Power-Good
■ Thermally Enhanced eTSSOP-20 exposed pad package
Applications
■ Broadband, networking and wireless communications
■ High-performance FPGAs, ASICs and microprocessors
■ Simple to design, high efficiency point of load regulation
from a 5V or 3.3V bus
Simplified Application Circuit
PowerWise® is a registered trademark of National Semiconductor Corporation.
© 2011 National Semiconductor Corporation 301521
30152101
www.national.com
Free Datasheet http://www.datasheet4u.com/
1 page  
Typical Performance Characteristics Unless otherwise specified: VVIN = 5V, VOUT = 1.2V, L= 0.56µH
(1.8mΩ RDCR), CSS = 33nF, fSW = 500 kHz, TA = 25°C for efficiency curves, loop gain plots and waveforms, and TJ = 25°C for all
others.
100
98
96
94
92
90
88
86
84
82
80
0
Efficiency
FSW = 500 kHz
FSW = 750 kHz
FSW = 1 MHz
3 6 9 12
OUTPUT CURRENT (A)
15
30152153
Efficiency
(VOUT = 2.5 V, fSW= 500 kHz , Inductor P/N SER2010-601MLD)
100
98
96
94
92
90
0
0.10
0.08
0.06
0.04
0.02
0.00
-0.02
-0.04
-0.06
-0.08
-0.10
3.0
VIN = 3.3V
VIN = 4.0V
VIN = 5.0V
VIN = 5.5V
3 6 9 12
OUTPUT CURRENT (A)
Line Regulation
IOUT = 0A
IOUT = 12A
3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
15
30152177
5.5
30152155
100
98
96
94
92
90
88
86
84
82
80
0
0.04
0.03
0.02
0.01
0.00
-0.01
-0.02
-0.03
-0.04
0
Efficiency
VOUT = 1.2V
VOUT = 3.3V
3 6 9 12
OUTPUT CURRENT (A)
Load Regulation
15
30152156
VIN = 3.3V
VIN = 5.0V
3 6 9 12
OUTPUT CURRENT (A)
15
30152154
Non-Switching IQTOTAL vs. VIN
1.5
1.4
1.3
1.2
1.1
1.0
3.0
3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
5.5
30152157
5 www.national.com
Free Datasheet http://www.datasheet4u.com/
5 Page 
SHORT-CIRCUIT PROTECTION
In the unfortunate event that the output is shorted with a low
impedance to ground, the LM21215A-1 will limit the current
into the short by resetting the device. A short-circuit condition
is sensed by a current-limit condition coinciding with a voltage
on the FB pin that is lower than 100 mV. When this condition
occurs, the device will begin its reset sequence, turning off
both power FETs and discharging the soft-start capacitor after
tRESETSS (nominally 110 µs). The device will then attempt to
restart. If the short-circuit condition still exists, it will reset
again, and repeat until the short-circuit is cleared. The reset
prevents excess current flowing through the FETs in a highly
inefficient manner, potentially causing thermal damage to the
device or the bus supply.
FIGURE 2. Current Limit Conditions
30152119
THERMAL PROTECTION
Internal thermal shutdown circuitry is provided to protect the
integrated circuit in the event that the maximum junction tem-
perature is exceeded. When activated, typically at 165°C, the
LM21215A-1 tri-states the power FETs and resets soft start.
After the junction cools to approximately 155°C, the device
starts up using the normal start up routine. This feature is
provided to prevent catastrophic failures from accidental de-
vice overheating. Note that thermal limit will not stop the die
from operating above the specified operating maximum tem-
perature,125°C. The die should be kept under 125°C to guar-
antee correct operation.
POWERGOOD FLAG
The PGOOD pin provides the user with a way to monitor the
status of the LM21215A-1. In order to use the PGOOD pin,
the application must provide a pull-up resistor to a desired DC
voltage (i.e. Vin). PGOOD will respond to a fault condition by
pulling the PGOOD pin low with the open-drain output.
PGOOD will pull low on the following conditions – 1) VFB
moves above or below the VOVP or VUVP, respectively 2) The
enable pin is brought below the enable threshold 3) The de-
vice enters a pre-biased output condition (VFB>VSS).
Figure 3 shows the conditions that will cause PGOOD to fall.
11 www.national.com
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
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| PDF Descargar | [ Datasheet LM21215A-1.PDF ] | |
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