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PDF LTC3865 Data sheet ( Hoja de datos )
| Número de pieza | LTC3865 | |
| Descripción | Dual 2-Phase Synchronous DC/DC Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Features
n Dual, 180° Phased Controllers
n 2-Pin VID Output Voltage Programming from 0.6V
to 5V
n High Efficiency: Up to 95%
n RSENSE or DCR Current Sensing
n Phase-Lockable Fixed Frequency 250kHz to 770kHz
n Adjustable Current Limit
n Dual N-Channel MOSFET Synchronous Drive
n Wide VIN Range: 4.5V to 38V Operation
n Adjustable Soft-Start Current Ramping or Tracking
n Output OV Protection With Reverse Current Limit
n Power Good Output Voltage Monitor
n 32-Pin 5mm × 5mm QFN and 38-Lead TSSOP
Packages
Applications
n DC Power Distribution Systems
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, µModule, Linear Technology and the Linear logo
are registered trademarks and No RSENSE is a trademark of Linear Technology Corporation. All
other trademarks are the property of their respective owners. U.S. Patents, including 5481178,
5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258.
LTC3865w/wLwT.DCataS3he8et46U.c5om-1
Dual, 2-Phase Synchronous
DC/DC Controller with
Pin Selectable Outputs
Description
The LTC®3865/LTC3865-1 are high performance dual
synchronous step-down DC/DC switching regulator
controllers that drive all N‑channel synchronous power
MOSFET stages. A constant frequency current mode
architecture allows a phase-lockable frequency of up to
770kHz. Power loss and noise are minimized by operating
the two controller output stages out of phase.
OPTI-LOOP® compensation allows the transient response
to be optimized over a wide range of output capacitance
and ESR values. Independent track/soft-start pins for
each controller ramp the output voltage during start-up.
Current foldback limits MOSFET heat dissipation during
short-circuit conditions. The MODE/PLLIN pin selects
among Burst Mode® operation, pulse-skipping mode,
and continuous inductor current mode. The output volt-
ages can be precisely programmed by pin strapping or
external resistors.
The LTC3865/LTC3865-1 are available in low profile (5mm
× 5mm) 32-pin QFN and 38-Lead thermally enhanced
TSSOP packages.
Typical Application
VOUT1
1.5V
15A
High Efficiency 1.5V/15A, 1.2V/15A Step-Down Converter
2.2Ω
+
22µF
VIN
4.5V TO 24V
50V
1µF
0.47µH
2mΩ
+
100µF
COUT2,3
4.7µF
0.1µF
100Ω
1000pF
100Ω
1000pF
10k
100pF
VIN INTVCC
TG1 TG2
BOOST1
SW1
BG1
LTC3865
BOOST2
SW2
BG2
SENSE1+
PGND
FREQ
SENSE2+
SENSE1–
VID11
VID12
VOSENSE1
ITH1
TK/SS1
SGND
SENSE2–
VID21
VID22
VOSENSE2
ITH2
TK/SS2
0.1µF 0.1µF
0.1µF
0.47µH
100Ω
1000pF
2mΩ
100Ω
1000pF
162k 15k
+
100pF
COUT5,6
VOUT2
1.2V
15A
100µF
Efficiency and Power Loss
vs Load Current
100
90
VIN = 12V
VOUT = 1.5V
80
10
70
EFFICIENCY
1
60
50 POWER LOSS
40
30 0.1
20
10
0
0.01
0.1 1
10
LOAD CURRENT (A)
0.01
100
3865 TA01b
3865 TA01a
3865f
1 page  
LTC3865w/wLwT.DCataS3he8et46U.c5om-1
E lectrical Characteristics The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at TJ = 25°C. VIN = 15V, VRUN1,2 = 5V unless otherwise noted.
SYMBOL PARAMETER
BG RDOWN
TG1,2 tr
TG1,2 tf
BG Driver Pull-Down On-Resistance
TG Transition Time:
Rise Time
Fall Time
BG1,2 tr
BG1,2 tf
BG Transition Time:
Rise Time
Fall Time
TG/BG t1D Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
BG/TG t2D Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
tON(MIN)
Minimum On-Time
INTVCC Linear Regulator
VINTVCC
Internal VCC Voltage
VLDO INT INTVCC Load Regulation
VEXTVCC
EXTVCC Switchover Voltage
VLDO EXT EXTVCC Voltage Drop
VLDOHYS
EXTVCC Hysteresis
Oscillator and Phase-Locked Loop
fNOM Nominal Frequency
fLOW Lowest Frequency
fHIGH Highest Frequency
RMODE/PLLIN MODE/PLLIN Input Resistance
IFREQ
Frequency Setting Current
PGOOD OUTPUT
VPGL
IPGOOD
VPG
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
tPG PGOOD Bad Blanking Time
CONDITIONS
BG Low
(Note 6)
CLOAD = 3300pF
CLOAD = 3300pF
(Note 6)
CLOAD = 3300pF
CLOAD = 3300pF
CLOAD = 3300pF Each Driver
CLOAD = 3300pF Each Driver
(Note 7)
6V < VIN < 38V
ICC = 0mA to 20mA
EXTVCC Ramping Positive
ICC = 20mA, VEXTVCC = 5V
RFREQ = 162k
RFREQ = 0Ω
RFREQ ≥ 325k
IPGOOD = 2mA
VPGOOD = 5V
VVOIDS1EN1S=E
with Respect to Set Regulated Voltage
VID12 = VID21 = VID22 = Float
VOSENSE Ramping Negative
VOSENSE Ramping Postitive
Measured from VID Transitition Edge
MIN TYP MAX UNITS
1.4 Ω
25 ns
25 ns
25 ns
25 ns
30 ns
30 ns
90 ns
4.8 5.0 5.2
0.5 2
l 4.5
4.7
50 100
200
V
%
V
mV
mV
450 500 550
210 250 290
650 770 880
250
6.5 7.5 8.5
kHz
kHz
kHz
kΩ
µA
0.1 0.3
±2
V
µA
–7 –10 –12.5
7 10 12.5
100
%
%
µs
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 LTC3865E/LTC3865E-1 are guaranteed to meet performance
specifications over the 0°C to 85°C operating junction temperature range.
Specifications over the –40°C to 85°C operating junction temperature
range are assured by design, characterization and correlation with
statistical process controls. The LTC3865I/LTC3865I-1 are guaranteed to
meet performance specifications over the full –40°C to 125°C operating
junction temperature range. Note that the maximum ambient temperature
is determined by specific operating conditions in conjunction with board
layout, the rated package thermal resistance and other environmental
factors.
Note 3: TJ is calculated from the ambient temperature TA and power
dissipation PD according to the following formulas:
LTC3865UH: TJ = TA + (PD • 34°C/W)
LTC3865FE: TJ = TA + (PD • 25°C/W)
Note 4: The LTC3865/LTC3865-1 are tested in a feedback loop that servos
VITH1,2 to a specified voltage and measures the resultant VOSENSE1,2.
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 6: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7: The minimum on-time condition is specified for an inductor peak-
to-peak ripple current 40% of IMAX (see Minimum On-Time Considerations
in the Applications Information section).
Note 8: VSENSE(MAX) defaults to 50mV for the LTC3865-1.
3865f
5 Page 
FUNCTIONAL Diagram
LTC3865w/wLwT.DCataS3he8et46U.c5om-1
FREQ/FREQ
7.5µA
PLL-SYNC
AND
LPF
MODE/PLLIN
MODE/SYNC
DETECT
VID1
VID2
INPUT VID LOGIC
AND
RESISTIVE DIVIDERS
EXTVCC
4.7V
–+
0.6V F
–+
F
5V
REG
OSC
+
ICMP
–
3k
S
RQ
–
IREV
+
FCNT
BURSTEN
ON SWITCH
LOGIC
AND
ANTI-
SHOOT
THROUGH
RUN
OV
ILIM SLOPE COMPENSATION
INTVCC
UVLO
1 SLOPE RECOVERY
51k ACTIVE CLAMP
ITHB
VIN
+ VIN
CIN
INTVCC
BOOST
TG CB
SW
SENSE+
DB
SENSE–
BG
CVCC
PGND
PGOOD
+
UV
–
0.54V
VOSENSE
SGND
INTVCC
M1
L1
VOUT
+
COUT
M2
VIN SLEEP
0.6V
REF
–+
0.55V
EA
– SS +
0.5V
– RUN +
1.2V
1.3µA
+
OV
–
VFB
0.66V
1µA
ITH RC CC1
RUN TK/SS CSS
3865 FBD
3865f
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC3865.PDF ] | |
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