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| LTC3851_15 Datasheet, PDF (4/28 Pages) Linear Technology – Synchronous Step-Down Switching Regulator Controller | |||
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LTC3851
ELECTRICAL CHARACTERISTICS The l denotes the speciï¬cations which apply over the full operating
temperature range, otherwise speciï¬cations are at TA = 25°C. VIN = 15V, VRUN = 5V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Oscillator and Phase-Locked Loop
fNOM
fLOW
fHIGH
RMODE/PLLIN
Nominal Frequency
Lowest Frequency
Highest Frequency
MODE/PLLIN Input Resistance
RFREQ = 60k
RFREQ = 160k
RFREQ = 36k
480
500
530
kHz
220
250
280
kHz
710
750
790
kHz
100
kΩ
fMODE
IFREQ
MODE/PLLIN Minimum Input Frequency VMODE = External Clock
MODE/PLLIN Maximum Input Frequency VMODE = External Clock
Phase Detector Output Current
Sinking Capability
Sourcing Capability
fMODE > fOSC
fMODE < fOSC
250
kHz
750
kHz
â10
μA
10
μA
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 LTC3851E is guaranteed to meet performance speciï¬cations
from 0°C to 85°C. Speciï¬cations over the â40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3851I is guaranteed to meet
speciï¬cations over the â40°C to 125°C operating temperature range.
Note 3: TJ is calculated from the ambient temperature TA and power
dissipation PD according to the following formulas:
LTC3851GN: TJ = TA + (PD ⢠110°C/W)
LTC3851UD: TJ = TA + (PD ⢠68°C/W)
LTC3851MSE: TJ = TA + (PD ⢠40°C/W)
Note 4: The LTC3851 is tested in a feedback loop that servos VITH to a
speciï¬ed voltage and measures the resultant VFB.
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 speciï¬ed for an inductor
peak-to-peak ripple current ~40% of IMAX (see Minimum On-Time
Considerations in the Applications Information section).
TYPICAL PERFORMANCE CHARACTERISTICS
Efï¬ciency vs Output Current
and Mode
100
VIN = 12V
90 VOUT = 1.5V
80
BURST
70
60
PULSE
SKIP
50
40
CCM
30
20
10
0
10
100
1000 10000 100000
LOAD CURRENT (mA)
3851 G01
Efï¬ciency vs Output Current
and Mode
100
90
BURST
80
70
60
PULSE
50
SKIP
CCM
40
30
20
10
0
10
VIN = 12V
VOUT = 3.3V
FIGURE 11 CIRCUIT
100
1000 10000
LOAD CURRENT (mA)
100000
3851 G02
Efï¬ciency vs Output Current
and Mode
100
90
80
BURST
70
60 PULSE
SKIP
50
CCM
40
30
20
10
0
10
VIN = 12V
VOUT = 5V
100
1000 10000 100000
LOAD CURRENT (mA)
3851 G03
3851fb
4
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