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PDF LTC3862-2 Data sheet ( Hoja de datos )
| Número de pieza | LTC3862-2 | |
| Descripción | Multi-Phase Current Mode Step-Up DC/DC Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Features
n Wide VIN Range: 5.5V to 36V Operation
n 2-Phase Operation Reduces Input and Output
Capacitance
n Fixed Frequency, Peak Current Mode Control
n Internal 10V LDO Regulator
n Lower UVLO Thresholds Allows the Use of
MOSFETs Rated at 6V VGS
n Adjustable Slope Compensation Gain
n Adjustable Max Duty Cycle (Up to 96%)
n Adjustable Leading Edge Blanking
n ±1% Internal Voltage Reference
n Programmable Operating Frequency with One
External Resistor (75kHz to 500kHz)
n Phase-Lockable Fixed Frequency 50kHz to 650kHz
n SYNC Input and CLKOUT for 2-, 3-, 4-, 6- or
12-Phase Operation (PHASEMODE Programmable)
n 24-Lead Narrow SSOP Package
n 5mm × 5mm QFN Package with 0.65mm Lead Pitch
n 24-Lead Thermally Enhanced TSSOP Package
Applications
n Automotive, Telecom and Industrial Power Supplies
LTC3862-2
Multi-Phase Current Mode
Step-Up DC/DC Controller
Description
The LTC®3862-2 is a two-phase constant frequency, current
mode boost and SEPIC controller that drives N-channel
power MOSFETs. Two-phase operation reduces system
filtering capacitance and inductance requirements.
The operating frequency can be set with an external resistor
over a 75kHz to 500kHz range and can be synchronized
to an external clock using the internal PLL. Multiphase
operation is possible using the SYNC input, the CLKOUT
output and the PHASEMODE control pin allowing 2-, 3-,
4-, 6- or 12-phase operation.
Other features include an internal 10V LDO with under-
voltage lockout protection for the gate drivers, a preci-
sion RUN pin threshold with programmable hysteresis,
soft-start and programmable leading edge blanking and
maximum duty cycle.
PART NUMBER
LTC3862
LTC3862-1
LTC3862-2
INTVCC
5V
10V
10V
VIN ON
3.3V
7.5V
4.4V
VIN OFF
2.9V
7.0V
3.9V
L, LT, LTC, LTM, Linear Technology, the Linear logo and PolyPhase are registered trademarks
and No RSENSE and ThinSOT are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents, including
6144194, 6498466, 6611131.
Typical Application
796k
100k
24.9k
4.7µF
110k
0.1µF
1nF
10nF
12.4k 12.1k
220pF
VIN
RUN GATE1
INTVCC SENSE1+
LTC3862-2
BLANK
FREQ
SYNC
PLLFLTR
SENSE1–
GATE2
SENSE2+
SS SENSE2–
3V8 PGND
CLKOUT
FB SLOPE
DMAX
ITH PHASEMODE
SGND
16µH 16µH
0.0033Ω
210µF
100V
22µF
50V
VIN
6V TO 32V
VOUT
80V
7A (MAX)
0.0033Ω
38622 TA01a
For more information www.linear.com/LTC3862-2
Efficiency vs Output Current
97 VOUT = 80V
95
93
91
89
87
85
83
81
79
77
10
VIN = 6V
VIN = 9V
VIN = 12V
VIN = 24V
100 1000
LOAD CURRENT (mA)
10000
38622 TA01b
38622fa
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1 page  
LTC3862-2
E lectrical Characteristics (Notes 2, 3) The l denotes the specifications which apply over the
specified operating junction
otherwise noted.
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, RUN = 2V and SS = open, unless
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
tON(MIN)1
tON(MIN)2
tON(MIN)3
Gate Driver
Minimum On-Time
Minimum On-Time
Minimum On-Time
VBLANK = 0V (Note 8)
VBLANK = Float (Note 8)
VBLANK = 3V8 (Note 8)
210 ns
290 ns
375 ns
RDS(ON)
Overvoltage
Driver Pull-Up RDS(ON)
Driver Pull-Down RDS(ON)
3Ω
0.9 Ω
VFB(OV)
VFB, Overvoltage Lockout Threshold
VFB(OV) – VFB(NOM) in Percent
8 10 12
%
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.
Note 3: The LTC3862E-2 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3862I-2 is guaranteed over the
full –40°C to 125°C operating temperature range and the LTC3862H-2 is
guaranteed over the full –40°C to 150°C operating temperature range.
High junction temperatures degrade operating lifetimes. Operating lifetime
is derated at junction temperatures greater than 125°C.
Note 4: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Continuous
operation above the specified maximum operating junction temperature
may impair device reliability.
Note 5: Supply current in normal operation is dominated by the current
needed to charge the external MOSFET gates. This current will vary with
supply voltage and the external MOSFETs used.
Note 6: The IC is tested in a feedback loop that adjusts VFB to achieve a
specified error amplifier output voltage.
Note 7: Guaranteed by design, not subject to test.
Note 8: The minimum on-time condition is specified for an inductor peak-
to-peak ripple current = 30% (see Minimum On-Time Considerations in the
Applications Information section).
Note 9: The maximum duty cycle limit is derived from an internal
clock that runs at 12× the programmed switching frequency. See the
Applications Information section for additional information.
For more information www.linear.com/LTC3862-2
38622fa
5
5 Page 
LTC3862-2
Pin Functions (SSOP/QFN/TSSOP)
SENSE2+ (Pin 13/Pin 11/Pin 13): Positive Inputs to the
Current Comparators. The ITH pin voltage programs the
current comparator offset in order to set the peak current
trip threshold. This pin is normally connected to a sense
resistor in the source of the power MOSFET.
SENSE1– (Pin 22/Pin 20/Pin 22): Negative Inputs to the
Current Comparators. This pin is normally connected to
the bottom of the sense resistor.
SENSE2– (Pin 14/Pin 12/Pin 14): Negative Inputs to the
Current Comparators. This pin is normally connected to
the bottom of the sense resistor.
SGND (Pin 9/Pin 7/Pin 9): Signal Ground. All feedback and
soft-start connections should return to SGND. For optimum
load regulation, the SGND pin should be kelvin connected
to the PCB location between the negative terminals of the
output capacitors.
SLOPE (Pin 2/Pin 24/Pin 2): This pin programs the gain
of the internal slope compensation. Floating this pin
provides a normalized slope compensation gain of 1.00.
Connecting this pin to 3V8 increases the normalized
slope compensation by 66%, and connecting it to SGND
decreases the normalized slope compensation by 37.5%.
See the Applications Information section for more details.
SS (Pin 6/Pin 4/Pin 6): Soft-Start Input. For soft-start
operation, connecting a capacitor from this pin to SGND
will clamp the output of the error amp. An internal 5µA
current source will charge the capacitor and set the rate
of increase of the peak switch current of the converter.
SYNC (Pin 11/Pin 9/Pin 11): PLL Synchronization Input.
Applying an external clock between 50kHz and 650kHz
will cause the operating frequency to synchronize to the
clock. SYNC is pulled down by a 50k internal resistor. The
rising edge of the SYNC input waveform will align with the
rising edge of GATE1 in closed-loop operation. A SYNC
signal with an amplitude greater than 1.6V is considered
an active high, while any signal below 0.9V is considered
an active low.
VIN (Pin 20/Pin 18/Pin 20): Main Supply Input. A low ESR
ceramic capacitor should be connected between this pin
and SGND.
For more information www.linear.com/LTC3862-2
38622fa
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11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC3862-2.PDF ] | |
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