|
|
PDF LT3782 Data sheet ( Hoja de datos )
| Número de pieza | LT3782 | |
| Descripción | 2-Phase Step-Up DC/DC Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LT3782 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
LT3782
2-Phase Step-Up
DC/DC Controller
FEATURES
■ 2-Phase Operation Reduces Required Input and
Output Capacitance
■ Programmable Switching Frequency:
150kHz to 500kHz
■ 6V to 40V Input Range
■ 10V Gate Drive with VCC ≥13V
■ High Current Gate Drive (4A)
■ Programmable Soft-Start and Current Limit
■ Programmable Slope Compensation for
High Noise Immunity
■ MOSFET Gate Signals with Programmable
Falling Edge Delay for External Synchronous
Drivers
■ Programmable Undervoltage Lockout
■ Programmable Duty Cycle Clamp (50% or Higher)
■ Thermally Enhanced 28-Lead SSOP Package
U
APPLICATIO S
■ Industrial Equipment
■ Telecom Infrastructure
■ Interleaved Isolated Power Supply
DESCRIPTIO
The LT®3782 is a current mode two phase step-up DC/DC
converter controller. Its high switching frequency (up to
500kHz) and 2-phase operation reduce system filtering
capacitance and inductance requirements.
With 10V gate drive (VCC ≥13V) and 4A peak drive current,
the LT3782 can drive most industrial grade high power
MOSFETs with high efficiency. For synchronous applica-
tions, the LT3782 provides synchronous gate signals with
programmable falling edge delay to avoid cross conduc-
tion when using external MOSFET drivers. Other features
include programmable undervoltage lockout, soft-start,
current limit, duty cycle clamp (50% or higher) and slope
compensation.
The LT3782 is available in a thermally enhanced 28-lead
SSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6144194.
TYPICAL APPLICATIO
50V 4A Boost Converter
VIN
10V TO 36V
CIN
10µF
50V
2x
100pF
R6
825k
R8
274k
VCC
1µF
RUN
GBIAS1
GBIAS2
GBIAS
BGATE1
LT3782
RSLOPE
59k
RFREQ
80k
SLOPE
DELAY
DCL
RSET
VEE1
BGATE2
VEE2
0.1µF
SS
SENSE1+
VC
13k
6.8nF
SENSE1–
SENSE2+
SENSE2–
GND FB
L1
+ C3 L2
2µF
D1
30BQ060
M1
Si7852dp
2x
D2
30BQ060
RS1
0.004Ω
M2
Si7852dp
2x
RS2
0.004Ω
COUT1
10µF
50V
2x +
VOUT
50V, 4A
COUT2
220µF
L1, L2: PB2020.223
CIN, COUT1: X7R, TDK
10Ω 10Ω
10nF
10nF
RF1
475k
3782 TA01
RF2
24.9k
Efficiency and Power Loss
vs Load Current
97 18
EFFICIENCY
VIN = 24V
95 15
VIN = 12V
93 12
91
VIN = 12V
9
89 VIN = 24V 6
POWER LOSS
87 3
85 0
012345
IOUT (A)
3782 TA01b
3782fa
1
1 page  
LT3782
PI FU CTIO S
SGATE2 (Pin 1): Second Phase Synchronous Drive Sig-
nal. An external driver buffer is needed to drive the top
synchronous power FET.
SGATE1 (Pin 2): First Phase Synchronous Drive Signal.
An external driver buffer is needed to drive the top syn-
chronous power FET.
NC (Pin 3): Not Connected. Can be connected to GND.
GND (Pin 4): Chip Ground.
SYNC (Pin 5): Synchronization Input. The pulse width can
range from 10% to 70%. Note that the operating frequency
is half of the sync frequency.
DELAY (Pin 6): When synchronous drivers are used, the
programmable delay that delays BGATE turns on after
SGATE turns off.
DCL (Pin 7): This pin programs the limit of the maximum
duty cycle. When connected to VRSET, it operates at natural
maximum duty cycle, approximately 90%.
SENSE1+ (Pin 8): First Phase Current Sense Amplifier
Positive Input. An RC filter is required across the current
sense resistor. Current limit threshold is set at 60mV.
SENSE1– (Pin 9): First Phase Current Sense Amplifier
Negative Input. An RC filter is required across the current
sense resistor.
SLOPE (Pin 10): A resistor from SLOPE to GND increases
the internal current mode PWM slope compensation.
RSET (Pin 11): A resistor from RSET to GND sets the
oscillator charging current and the operating frequency.
SENSE2– (Pin 12): Second Phase Current Sense Amplifier
Negative Input. An RC filter is required across the current
sense resistor.
SENSE2+ (Pin 13): Second Phase Current Sense Amplifier
Positive Input. An RC filter is required across the current
sense resistor. Current limit threshold is set at 60mV.
SS (Pin 14): Soft-Start. A capacitor on this pin sets the
output ramp up rate. The typical time for SS to reach the
programmed level is (C • 2.44V)/10µA.
VC (Pin 15): The output of the gm error amplifier and the
control signal of the current loop of the current-mode
PWM. Switching starts at 0.7V, and higher VC voltages
corresponds to higher inductor current.
FB (Pin 16): Error Amplifier Inverting Input. A resistor
divider to this pin sets the output voltage.
RUN (Pin 17): LT3782 goes into shutdown mode when
VRUN is below 2.2V and goes to low bias current shutdown
mode when VRUN is below 0.3V.
NC (Pin 18): Not Connected. Can be connected to GND.
VEE2 (Pin 19): Gate Driver BGATE2 Ground. This pin
should be connected to the ground side of the second
current sense resistor.
BGATE2 (Pin 20): Second Phase MOSFET Driver.
GBIAS2 (Pin 21): Bias for Gate Driver BGATE2. Should be
connected to GBIAS or an external power supply between
12V to 14V. A bypass low ESR capacitor of 2µF or larger
is needed and should be connected directly to the pin to
minimize parasitic impedance.
GBIAS1 (Pin 22): Bias for Gate Driver BGATE1. Should be
connected to GBIAS2.
BGATE1 (Pin 23): First Phase MOSFET Driver.
VEE1 (Pin 24): Gate Driver BGATE1 Ground. This pin
should be connected to the ground side of the second
current sense resistor.
NC (Pin 25): Not Connected. Can be connected to GND.
NC (Pin 26): Not Connected. Can be connected to GND.
VCC (Pin 27): Chip Power Supply. Good supply bypassing
is required.
GBIAS (Pin 28): Internal 11V regulator output for biasing
internal circuitry. Should be connected to GBIAS1 AND
GBIAS2.
EXPOSED PAD (Pin 29): The exposed package pad is
fused to internal ground and is for heat sinking. Solder the
bottom metal plate onto expanded ground plane for opti-
mum thermal performance.
3782fa
5
5 Page 
LT3782
APPLICATIO S I FOR ATIO
From a known power dissipated in the power MOSFET, its
junction temperature can be obtained using the following
formula:
TJ = TA + PFET • RTH(JA)
The RTH(JA) to be used in this equation normally includes
the RTH(JC) for the device plus the thermal resistance from
the case to the ambient temperature (RTH(CA)). This value
of TJ can then be compared to the original, assumed value
used in the iterative calculation process.
Input Capacitor Choice
The input capacitor must have high enough voltage and
ripple current ratings to handle the maximum input volt-
age and RMS ripple current rating. The input ripple current
in a boost circuit is very small because the input current is
continuous. With 2-phase operation, the ripple cancella-
Normalized Peak-to-Peak Input
Ripple Current
1.00
0.90
0.80
0.70
0.60
1-PHASE
0.50
0.40
2-PHASE
0.30
0.20
0.10
0
0 0.2 0.4 0.6 0.8 1.0
DUTY CYCLE
3782 F04
Figure 5. Normalized Input Peak-to-Peak Ripple Current:
Inorm
=
VIN
L • fs
The RMS Ripple Current is About 29% of the Peak-to-Peak
Ripple Current.
tion will further reduce the input capacitor ripple current
rating. The ripple current is plotted in Figure 5. Please note
that the ripple current is normalized against
Inorm
=
VIN
L • fs
Output Capacitor Selection
The voltage rating of the output capacitor must be greater
than the maximum output voltage with sufficient derating.
Because the ripple current in output capacitor is a pulsat-
ing square wave in a boost circuit, it is important that the
ripple current rating of the output capacitor be high
enough to deal with this large ripple current. Figure 6
shows the output ripple current in the 1- and 2-phase
designs. As we can see, the output ripple current of a
2-phase boost circuit reaches almost zero when the duty
cycle equals 50% or the output voltage is twice as much
as the input voltage. Thus the 2-phase technique signifi-
cantly reduces the output capacitor size.
3.25
3.00
2.75
2.50
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
0.1
Normalized Output RMS
Ripple Currents
1-PHASE
2-PHASE
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
DUTY CYCLE OR (1-VIN/VOUT)
3782 F05
Figure 6. Normalized Output Ripple Currents in Boost Converter:
1-Phase and 2-Phase. IOUT Is the DC Output Current.
3782fa
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT3782.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LT3781 | Bootstrap Start Dual Transistor Synchronous Forward Controller | Linear Technology |
| LT3782 | 2-Phase Step-Up DC/DC Controller | Linear Technology |
| LT3782A | 2-Phase Step-Up DC/DC Controller |  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 |