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LTC3646-1 데이터시트 PDF




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부품번호 LTC3646-1 기능
기능 1A Synchronous Step-Down Converter
제조업체 Linear
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LTC3646-1 데이터시트, 핀배열, 회로
FEATURES
nn Wide Input Voltage Range: 4.0V to 40V
nn 1A Guaranteed Output Current
nn High Efficiency: Up to 95%
nn Wide Output Voltage Range
nn LTC3646: 2.0V to 30V
nn LTC3646-1: 0.6V to 15V
nn ±1% Accurate Reference Voltage
nn Internal or External Compensation
nn Switching Frequency Adjustable and Synchronizable:
200kHz to 3MHz
nn Selectable High Efficiency Burst Mode® Operation or
Forced Continuous Mode
nn 14 Lead 3mm × 4mm DFN or Thermally Enhanced
16-Lead MSOP Packages
APPLICATIONS
nn Point of Load Power Supplies
nn Intermediate Bus Power
nn Automotive Applications
LTC3646/LTC3646-1
40V, 1A Synchronous
Step-Down Converter
DESCRIPTION
The LTC®3646 is a high efficiency, step-down DC/DC
converter with internal high side and synchronous power
FETs. It draws only 140µA typical DC supply current in
Burst Mode operation at no load while maintaining output
voltage regulation.
The LTC3646 can supply up to a 1A load, and its combina-
tion of Burst Mode operation, integrated power switches
and low quiescent current provides high efficiency over a
broad range of load currents. Alternatively, it can be used
in forced continuous mode for ripple sensitive applications.
The LTC3646 has a wide 4.0V to 40V input range and its
patented controlled on-time architecture and 0.6V refer-
ence voltage allow for large step-down ratios without
the risk of output overvoltage. The frequency may be set
between 200kHz and 3.0MHz with a program resistor or
synchronized to an external clock.
The internal soft-start, short-circuit protection and volt-
age rating make the LTC3646 a robust part ideal for high
voltage applications.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 6580258, 5481178,
5994885, 6304066, 5847554, 6476589, 6774611.
TYPICAL APPLICATION
VIN
40V MAX
10µF
4.7µF
PVIN
BOOST
SVIN
RUN
LTC3646
INTVCC
MODE/SYNC
SW
ITH
RT
EXTVCC
SWITCH
CONTROL
VON
0.6V
SGND
+–
PGND
VFB
0.1µF
3.3µH
VOUT
5V
1A
412k
15µF
56.2k
3646 TA01a
Efficiency Curve
100 VIN = 12V
90 f = 1MHz
80
VOUT = 5V
1.0
VOUT = 3.3V 0.8
70
60 0.6
50
40 0.4
30 VOUT = 5V
20
VOUT = 3.3V
0.2
10
0
0.001
0.01 0.1
LOAD CURRENT (A)
0
1
3646 TA01b
For more information www.linear.com/LTC3646
36461fc
1




LTC3646-1 pdf, 반도체, 판매, 대치품
LTC3646/LTC3646-1
E LECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2), PVIN = SVIN = 12V unless otherwise noted.
SYMBOL
tPGOOD
RPGOOD
tSS
VMODE/SYNC
PARAMETER
PGOOD Filter Time
PGOOD Pull-Down Resistance
PGOOD Leakage
Internal Soft-Start Time
Mode Threshold Voltage
SYNC Threshold Voltage
MODE/SYNC Input Current
CONDITIONS
RT = INTVCC
IPGOOD = 10mA
VPGOOD = VINTVCC
Mode
Mode
VVIIHL
SYNCIH
SYNCIL
MIN
15
l 1.2
l
l 1.2
l
TYP MAX UNITS
30 µs
63 Ω
1.0 µA
250 500
µs
V
0.3 V
V
0.3 V
12
µA
Internal ITH Voltage Threshold
VON Pin Input Impedance
LTC3646
LTC3646-1
l INTVCC – 0.3V
520
600
V
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: The LTC3646 is tested under pulsed load conditions such that
TJ ≈ TA. The LTC3646E is guaranteed to meet specifications from
0°C to 85°C junction temperature. Specifications over the –40°C to
125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC3646I is guaranteed over the –40°C to 125°C operating junction
temperature range and the LTC3646H is guaranteed over the –40°C to
150°C operating junction temperature range. High junction temperatures
derate operating lifetimes; operating lifetime is derated for junction
temperatures greater than 125°C. Note that the maximum ambient
temperature consistent with these specifications is determined by specific
operating conditions in conjunction with board layout, the rated package
thermal impedance and other environmental factors.
Note 3: Dynamic supply current is higher due to gate charging being
delivered at the switch frequency.
Note 4: Limits to VOUT are a subject to PVIN, SVIN, tON(MIN), tOFF(MIN),
and frequency constraints. See the Applications Information section for a
further discussion. These items are tested with appropriate combinations
of VIN, VON and frequency.
Note 5: RDS(ON) is guaranteed by correlation to wafer level measurements.
Note 6: Maximum allowed current draw when used as a regulated output
is 5mA. This supply is only intended to provide additional DC load current
as needed and not to regulate large transient or AC behavior as such
waveforms may impact LTC3646 operation.
Note 7: This IC includes overtemperature protection intended to protect
the device during momentary overload conditions. The maximum junction
temperature may be exceeded when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may result in device degradation or failure.
36461fc
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LTC3646-1 전자부품, 판매, 대치품
LTC3646/LTC3646-1
PIN FUNCTIONS (DFN/MSOP)
SGND (Pin 1/Pin 1): Analog Ground Pin. This pin should
have a low noise connection to the reference ground.
VFB (Pin 2/Pin 2): Output Voltage Feedback Pin. Input to
the error amplifier that compares the feedback voltage with
the internal 0.6V reference. Connect this pin to a resistor
divider network to program the desired output voltage.
ITH (Pin 3/Pin 3): Error Amplifier Output and Switching
Regulator Compensation Point. Connect this pin to appro-
priate external components to compensate the regulator
loop frequency response. Connect this pin to INTVCC to
use the default internal compensation.
RT (Pin 4/Pin 4): Oscillator Frequency Program Pin. Con-
nect an external resistor between 450k and 30k from this
pin to SGND to program the switching frequency from
200kHz to 3.0MHz. When RT is connected to INTVCC, the
switching frequency will be 2.25MHz. Do not float RT.
VON (Pin 5/Pin 5): On-Time Voltage Input Pin. This pin
provides information about the output voltage (VOUT) to
the on-time control loop. Connect this pin to the regulated
output to make the on-time proportional to the output
voltage.
PGOOD (Pin 6/Pin 6): Power Good Output Pin. PGOOD
is pulled to ground when the voltage at the VFB pin is not
within 7.5% (typical) of the internal 0.6V reference. PGOOD
becomes high impedance once the voltage at the VFB pin
returns to within 5% of the internal reference.
MODE/SYNC (Pin 7/Pin 7): Mode Selection and External
Clock Input Pin. This pin forces the LTC3646 into forced
continuous operation when tied to ground, and high ef-
ficiency Burst Mode operation when tied to INTVCC. When
driven with an external clock, the LTC3646 will adjust the
top switch on-time to match the switching frequency to
the applied clock frequency and the part will operate in
forced continuous mode. During start-up or external clock
synchronization, the operating mode will be as described
in the Applications Information section.
PVIN (Pin 8/Pins 9, 10): Supply Pin for the Power Switch.
This pin connects directly to top switch. Closely decouple
this pin to PGND with a 10µF or greater, low ESR capacitor.
SW (Pin 9/Pin 11): Switch Node Output Pin. Connect this
pin to the switch side of the external inductor and boost
capacitor.
BOOST (Pin 10/Pin 12): Boosted Supply Pin. A boosted
voltage is generated at this pin by connecting a capacitor
between this pin and the SW pin. The normal operation
voltage swing of this pin ranges from INTVCC to PVIN
+ INTVCC. When necessary, connect the cathode of an
external boost diode to this pin. See the Boost Capacitor
and Diode section.
INTVCC (Pin 11/Pin 13): Internal 5.0V Regulator Output
Pin. This pin should be decoupled to PGND with a 4.7µF or
greater low ESR capacitor. When necessary, connect the
anode of an external boost diode to this pin. The internal
regulator is disabled when the RUN pin is low.
EXTVCC (Pin 12/Pin 14): Use this input pin to power the
chip’s low voltage control circuitry if a high efficiency
supply between 4.5V and 6.0V is available. Otherwise,
connect this pin to SGND. See the Applications Informa-
tion section for further information.
RUN (Pin 13/Pin 15): Regulator Enable Pin. Enables chip
operation by applying a voltage greater than VRUN.
SVIN (Pin 14/Pin 16): Power Supply Input for Internal
Circuitry. Closely decouple this pin to SGND with a greater
than 1µF low ESR capacitor. SVIN pin voltage should equal
PVIN in order to correctly calculate on the on time and
maintain constant frequency operation.
PGND (Exposed Pad Pin 15/Exposed Pad Pin 17): Power
Ground Pin. The exposed pad must be well soldered to
the PCB ground to provide a low impedance electrical
connection to ground and rated thermal performance.
For more information www.linear.com/LTC3646
36461fc
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관련 데이터시트

부품번호상세설명 및 기능제조사
LTC3646-1

1A Synchronous Step-Down Converter

Linear
Linear

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