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PDF LTC3807 Data sheet ( Hoja de datos )
| Número de pieza | LTC3807 | |
| Descripción | Synchronous Step-Down Controller | |
| Fabricantes | Linear | |
| Logotipo |  |
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LTC3807
Low IQ, Synchronous
Step-Down Controller with 24V
Output Voltage Capability
FEATURES
n Wide VIN Range: 4V to 38V (40V Abs Max)
n Low Operating IQ: 50μA
n Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
n RSENSE or DCR Current Sensing
n Phase-Lockable Frequency (75kHz to 750kHz)
n Programmable Fixed Frequency (50kHz to 900kHz)
n Selectable Continuous, Pulse-Skipping or Low Ripple
Burst Mode® Operation at Light Load
n Selectable Current Limit
n Very Low Dropout Operation: 99% Duty Cycle
n Adjustable Output Voltage Soft-Start or Tracking
n Power Good Output Voltage Monitor
n Output Overvoltage Protection
n Low Shutdown IQ: 14μA
n Internal LDO Powers Gate Drive from VIN or EXTVCC
n No Current Foldback During Start-Up
n Small 20-Pin 3mm × 4mm QFN and TSSOP Packages
APPLICATIONS
n Automotive Always-On Systems
n Battery Powered Digital Devices
n Distributed DC Power Systems
DESCRIPTION
The LTC®3807 is a high performance step-down switching
regulator DC/DC controller that drives an all N-channel
synchronous power MOSFET stage. A constant fre-
quency current mode architecture allows a phase-lockable
frequency of up to 750kHz.
The 50μA no-load quiescent current extends operating run
time in battery-powered systems. OPTI-LOOP® compensa-
tion allows the transient response to be optimized over
a wide range of output capacitance and ESR values. The
LTC3807 features a precision 0.8V reference and power
good output indicator. A wide 4V to 38V input supply range
encompasses a wide range of intermediate bus voltages
and battery chemistries. The output voltage of the LTC3807
can be programmed between 0.8V to 24V.
The TRACK/SS pin ramps the output voltages during
start-up. Current foldback limits MOSFET heat dissipation
during short-circuit conditions. The PLLIN/MODE pin se-
lects among Burst Mode operation, pulse-skipping mode,
or continuous conduction mode at light loads.
L, LT, LTC, LTM, OPTI-LOOP, Burst Mode, Linear Technology and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners. Patents, including 5481178, 5705919, 6611131, 6498466, 6580258,
7230497.
TYPICAL APPLICATION
High Efficiency 12V/10A Step-Down Converter
VIN
12.5V TO 38V
22µF
VIN INTVCC
LTC3807
2.2µF
60.4k
4.7nF
15.4k
47pF
FREQ
ITH
0.1µF
VOUT
TRACK/SS
EXTVCC
SGND
TG
BOOST
SW
BG
PGND
SENSE+
SENSE–
VFB
PGOOD
0.1µF
10µH
100k
INTVCC
4mΩ
150µF
VOUT
12V
10A
100k
6.98k
3807 TA01a
For more information www.linear.com/LTC3807
Efficiency and Power Loss vs
Output Current
100 VIN = 24V
90 VOUT = 12V
80
70
EFFICIENCY
10
1
60
50 POWER LOSS 0.1
40
30 0.01
20
10
0
0.0001 0.001
0.01 0.1
IOUT (A)
FIGURE 13 CIRCUIT
Burst Mode OPERATION
0.001
1 10
3807 TA01b
3807f
1
1 page  
LTC3807
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), VIN = 12V, VRUN = 5V, EXTVCC = 0V unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
PGOOD Leakage Current
PGOOD Trip Level
VPGOOD = 5V
VFB with Respect to Set Regulated Voltage
VFB Ramping Negative
Hysteresis
–13 –10
2.5
±1
–7
µA
%
%
VFB Ramping Positive
Hysteresis
7 10 13
2.5
%
%
Delay for Reporting a Fault
25 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 LTC3807 is tested under pulsed load conditions such that
TJ ≈ TA. The LTC3807E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3807I is guaranteed
over the –40°C to 125°C operating junction temperature range, the
LTC3807H is guaranteed over the –40°C to 150°C operating junction
temperature range and the LTC3807MP is tested and guaranteed over
the –55°C to 150°C operating junction temperature range. High junction
temperatures degrade 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: The junction temperature (TJ, in °C) is calculated from the ambient
temperature (TA, in °C) and power dissipation (PD, in Watts) according to
the formula:
TJ = TA + (PD • θJA), where θJA is 43°C/W for the QFN or 38°C/W for the
TSSOP.
Note 4: The LTC3807 is tested in a feedback loop that servos VITH to a
specified voltage and measures the resultant VFB. The specification at
85°C is not tested in production and is assured by design, characterization
and correlation to production testing at other temperatures (125°C for
the LTC3807E/LTC3807I, 150°C for the LTC3807H/LTC3807MP). For the
LTC3807MP, the specification at –40°C is not tested in production and is
assured by design, characterization and correlation to production testing
at –55°C.
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).
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency and Power Loss vs
Output Current
100 VIN = 12V
90 VOUT = 3.3V
BURST EFFICIENCY
80
10000
1000
70 FCM LOSS
60
100
50
40
PULSE-SKIPPING
LOSS
BURST LOSS
10
30
20
FCM EFFICIENCY
1
10
0
0.0001
PULSE-SKIPPING
EFFICIENCY
0.001 0.01 0.1
1
OUTPUT CURRENT (A)
0.1
10
FIGURE 12 CIRCUIT
3807 G01
Efficiency vs Output Current
100
90 VOUT = 8.5V
80
VOUT = 3.3V
70
60
50
40
30
20
Burst Mode OPERATION
10
0
VIN = 12V
0.0001 0.001 0.01 0.1
OUTPUT CURRENT (A)
1
FIGURES 12, 14 CIRCUITS
10
3807 G02
For more information www.linear.com/LTC3807
Efficiency vs Input Voltage
100
98 VOUT = 8.5V
96
94
92
90
88 VOUT = 3.3V
86
84
82
80
ILOAD = 2A
0 5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
FIGURES 12, 14 CIRCUITS
3807 G03
3807f
5
5 Page 
FUNCTIONAL DIAGRAM
PGOOD
0.88V
VFB
0.72V
FREQ
20µA
VCO CLK2
CLK1
PFD
PLLIN/MODE
ILIM
VIN
EXTVCC
100k
SYNC
DET
CURRENT
LIMIT
+
4.7V –
5.1V
LDO
EN
5.1V
LDO
EN
SGND
INTVCC
LTC3807
BOOST
INTVCC VIN
DB
DROP
OUT
TOP TG
DET BOT
SQ
TOP ON
SW
RQ
SHDN
SWITCH
INTVCC
LOGIC BOT
BG
PGND
CB
D
CIN
COUT
0.425V
+
–
SLEEP
ICMP
–+
2.7V
0.65V
+ IR
+– –
2mV
SENSE+
SENSE–
SLOPE COMP
EA 0.80V
TRACK/SS
VFB
OV
0.88V
ITH
7µA SHDN
RST FOLDBACK
2(VFB)
10µA
TRACK/SS
11V
SHDN
RUN
L RSENSE
RB
RA
CC
CC2 RC
CSS
3807 FD
VOUT
For more information www.linear.com/LTC3807
3807f
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC3807.PDF ] | |
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