|
|
PDF LT3980 Data sheet ( Hoja de datos )
| Número de pieza | LT3980 | |
| Descripción | Step-Down Switching Regulator | |
| Fabricantes | Linear | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LT3980 (archivo pdf) en la parte inferior de esta página. Total 24 Páginas | ||
|
No Preview Available !
LT3980
58V, 2A, 2.4MHz
Step-Down Switching Regulator
with 85µA Quiescent Current
Features
Description
■ Wide Input Range: Operation from 3.6V to 58V
■ Overvoltage Lockout Protects Circuits Through 80V
Transients
■ 2A Maximum Output Current
■ Low Ripple (<15mVP-P) Burst Mode® Operation:
IQ = 85µA at 12VIN to 3.3VOUT
■ Adjustable Switching Frequency: 100kHz to 2.4MHz
■ Low Shutdown Current: IQ < 1µA
■ Catch Diode Current Sense Protects Circuit Through
Short-Circuit and Input Overvoltage
■ Synchronizable Between 250kHz to 2MHz
■ Power Good Flag
■ Saturating Switch Design: 200mΩ On-Resistance
■ Thermal Protection
■ Soft-Start Capability
■ Small 16-Pin Thermally Enhanced MSOP and
3mm × 4mm DFN Packages
Applications
■ Automotive Battery Regulation
■ Distributed Supply Regulation
■ Industrial Supplies
■ Wall Transformer Regulation
The LT®3980 is an adjustable frequency (100kHz to
2.4MHz) monolithic buck switching regulator that accepts
input voltages up to 58V (80V transient). A high efficiency
200mΩ switch is included on the die along with a boost
Schottky diode and the necessary oscillator, control, and
logic circuitry. Current mode topology is used for fast
transient response and good loop stability. Catch diode
current sense (DA pin) protects the circuit during input
voltage transients even when a high switching frequency
is used. Low ripple Burst Mode operation maintains high
efficiency at low output currents while keeping output
ripple below 15mV in a typical application. In addition, the
LT3980 can further enhance low output current efficiency
by drawing bias current from the output when VOUT is
above 3V. Shutdown reduces input supply current to less
than 1µA while a resistor and capacitor on the RUN/SS
pin provide a controlled output voltage ramp (soft-start).
A power good flag signals when VOUT reaches 91% of
the programmed output voltage. The LT3980 is available
in 16-pin MSOP and 3mm × 4mm DFN packages with
exposed pads for low thermal resistance.
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
Typical Application
5V Step-Down Converter
VIN
6.5V TO 58V
TRANSIENT
TO 80V
OFF ON
VIN
RUN/SS
BD
BOOST
10µF
4.75k
1nF
97.6k
VC LT3980
RT
PG
SYNC GND
SW
DA
FB
VOUT
5V
2A
0.47µF 10µH
22pF
536k
100k
47µF
3980 TA01
For more information www.linear.com/LT3980
Efficiency, VOUT = 5V
95
90 VIN = 12V
85 VIN = 24V
80 VIN = 48V
75
70
65
60
55 f = 400kHz
D = DIODES, INC. SBR3U100LP
50
0 0.5 1 1.5
ILOAD (A)
2
3980 TA01b
3980fa
1
Free Datasheet http://www.Datasheet4U.com
1 page  
LT3980
Typical Performance Characteristics TA = 25°C unless otherwise noted.
Switch Voltage Drop
700
600
500
400
300
200
100
0
012
SWITCH CURRENT (A)
3
3980 G10
Boost Pin Current
vs Switch Current
120
105
90
75
60
45
30
15
0
012
SWITCH CURRENT (A)
3
3980 G11
Feedback Voltage
840
820
800
780
760
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3980 G12
Switching Frequency
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
RF = 32.4k
0.80
–50 –25 0
25 50 75 100
TEMPERATURE (°C)
125 150
3880 G13
Frequency Foldback
1200
1000
800
600
400
200
0
0 100 200 300 400 500 600 700 800 900
FB PIN VOLTAGE (mV)
3980 G14
3500 RT vs Frequency
3000
2500
2000
1500
1000
500
0
1 10 100
RESISTANCE (kΩ)
1000
3980 G15
Minimum Switch On-Time
240
220
200
180
160
140
120
100 ILOAD = 1A
–50 –25 0
25 50 75 100
TEMPERATURE (°C)
125 150
3980 G16
Soft-Start
7
6
5
4
3
2
1
0
0 0.5 1 1.5 2 2.5 3 3.5
RUN/SS PIN VOLTAGE (V)
3980 G17
For more information www.linear.com/LT3980
RUN/SS Pin Current
24
20
16
12
8
4
0
0
10 20 30 40 50
RUN/SS PIN VOLTAGE (V)
60
3980 G18
3980fa
5
Free Datasheet http://www.Datasheet4U.com
5 Page 
LT3980
Applications Information
Of course, such a simple design guide will not always re-
sult in the optimum inductor for your application. A larger
value inductor provides a slightly higher maximum load
current and will reduce the output voltage ripple. If your
load is lower than 2A, then you can decrease the value of
the inductor and operate with higher ripple current. This
allows you to use a physically smaller inductor, or one
with a lower DCR resulting in higher efficiency. There are
several graphs in the Typical Performance Characteristics
section of this data sheet that show the maximum load
current as a function of input voltage and inductor value
for several popular output voltages. Low inductance may
result in discontinuous mode operation, which is okay
but further reduces maximum load current. For details of
maximum output current and discontinuous mode oper-
ation, see Linear Technology Application Note 44. Finally,
for duty cycles greater than 50% (VOUT/VIN > 0.5), there
is a minimum inductance required to avoid subharmonic
oscillations. See AN19.
Input Capacitor
Bypass the input of the LT3980 circuit with a ceramic
capacitor of X7R or X5R type. Y5V types have poor
performance over temperature and applied voltage, and
should not be used. A 10µF to 22µF ceramic capacitor is
adequate to bypass the LT3980 and will easily handle the
ripple current. Note that larger input capacitance is required
when a lower switching frequency is used. If the input
power source has high impedance, or there is significant
inductance due to long wires or cables, additional bulk
capacitance may be necessary. This can be provided with
a lower performance electrolytic capacitor.
Step-down regulators draw current from the input sup-
ply in pulses with very fast rise and fall times. The input
capacitor is required to reduce the resulting voltage rip-
ple at the LT3980 and to force this very high frequency
switching current into a tight local loop, minimizing EMI.
A 10µF capacitor is capable of this task, but only if it is
placed close to the LT3980 and the catch diode (see the
PCB Layout section). A second precaution regarding the
ceramic input capacitor concerns the maximum input
voltage rating of the LT3980. A ceramic input capacitor
combined with trace or cable inductance forms a high
quality (under damped) tank circuit. If the LT3980 circuit
is plugged into a live supply, the input voltage can ring to
twice its nominal value, possibly exceeding the LT3980’s
voltage rating. This situation is easily avoided (see the Hot
Plugging Safety section).
For space sensitive applications, a 4.7µF ceramic ca-
pacitor can be used for local bypassing of the LT3980
input. However, the lower input capacitance will result in
increased input current ripple and input voltage ripple, and
may couple noise into other circuitry. Also, the increased
voltage ripple will raise the minimum operating voltage
of the LT3980 to ~3.7V.
Output Capacitor and Output Ripple
The output capacitor has two essential functions. Along
with the inductor, it filters the square wave generated by the
LT3980 to produce the DC output. In this role it determines
the output ripple, and low impedance at the switching
frequency is important. The second function is to store
energy in order to satisfy transient loads and stabilize the
LT3980’s control loop. Ceramic capacitors have very low
equivalent series resistance (ESR) and provide the best
ripple performance. A good starting value is:
COUT
=
100
VOUT fSW
where fSW is in MHz, and COUT is the recommended output
capacitance in µF. Use X5R or X7R types. This choice will
provide low output ripple and good transient response.
Transient performance can be improved with a higher value
capacitor if the compensation network is also adjusted
to maintain the loop bandwidth. A lower value of output
capacitor can be used to save space and cost but transient
performance will suffer. See the Frequency Compensation
section to choose an appropriate compensation network.
When choosing a capacitor, look carefully through the
data sheet to find out what the actual capacitance is under
operating conditions (applied voltage and temperature).
A physically larger capacitor, or one with a higher voltage
rating, may be required. High performance tantalum or
electrolytic capacitors can be used for the output capacitor.
Low ESR is important, so choose one that is intended for
For more information www.linear.com/LT3980
3980fa
11
Free Datasheet http://www.Datasheet4U.com
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LT3980.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LT3980 | Step-Down Switching Regulator | Linear |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |