LTC3851A-1_15 Datasheet, PDF (4/30 Pages) Linear Technology – Synchronous Step-Down Switching Regulator Controller

LTC3851A-1
Electrical Characteristics The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T_A = 25°C (Note 2). V_IN = 15V, V_RUN = 5V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Oscillator and Phase-Locked Loop
f_NOM
Nominal Frequency
R_FREQ = 60k
460
500
540
kHz
f_LOW
f_HIGH
R_MODE/PLLIN
Lowest Frequency
Highest Frequency
MODE/PLLIN Input Resistance
R_FREQ = 160k
R_FREQ = 36k
205
235
265
kHz
690
750
810
kHz
100
kΩ
f_MODE
I_FREQ
MODE/PLLIN Minimum Input Frequency V_MODE = External Clock
MODE/PLLIN Maximum Input Frequency V_MODE = External Clock
Phase Detector Output Current
Sinking Capability
Sourcing Capability
f_MODE > f_OSC
f_MODE < f_OSC
250
kHz
750
kHz
–90
µA
75
µA
PGOOD Output
V_PGL
I_PGOOD
V_PG
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
I_PGOOD = 2mA
V_PGOOD = 5V
V_FB with Respect to Set Regulated Voltage
V_FB Ramping Negative (UV)
V_FB Ramping Positive (OV)
0.1
0.3
V
±1
µA
–12.5 –10 –7.5
%
7.5
10
12.5
%
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 LTC3851A-1 is tested under pulsed load conditions such that
T_A ≈ T_J. The LTC3851AE-1 is guaranteed to meet performance
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 LTC3851AI-1 is guaranteed to meet specifications over the –40°C
to 125°C operating junction temperature range, the LTC3851AH-1 is
guaranteed over the –40°C to 150°C operating junction temperature range
and the LTC3851AMP-1 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: T_J is calculated from the ambient temperature T_A and power
dissipation P_D according to the following formulas:
LTC3851AMSE-1: T_J = T_A + (P_D • 40°C/W)
LTC3851AUD-1: T_J = T_A + (P_D • 68°C/W)
Note 4: The LTC3851A-1 is tested in a feedback loop that servos V_ITH to a
specified voltage and measures the resultant V_FB.
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. Rise and fall times are assured by
design, characterization and correlation with statistical process controls.
Note 7: The minimum on-time condition is specified for an inductor
peak-to-peak ripple current ~40% of I_MAX (see Minimum On-Time
Considerations in the Applications Information section).
Note 8: Guaranteed by design; not tested in production.
3851a1fa
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