LTC3851A-1
4
3851a1fa
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
Lowest Frequency R
FREQ
= 160k 205 235 265 kHz
f
HIGH
Highest Frequency R
FREQ
= 36k 690 750 810 kHz
R
MODE/PLLIN
MODE/PLLIN Input Resistance 100
kΩ
f
MODE
MODE/PLLIN Minimum Input Frequency
MODE/PLLIN Maximum Input Frequency
V
MODE
= External Clock
V
MODE
= External Clock
250
750
kHz
kHz
I
FREQ
Phase Detector Output Current
Sinking Capability
Sourcing Capability
f
MODE
> f
OSC
f
MODE
< f
OSC
–90
75
µA
µA
PGOOD Output
V
PGL
PGOOD Voltage Low I
PGOOD
= 2mA 0.1 0.3 V
I
PGOOD
PGOOD Leakage Current V
PGOOD
= 5V ±1 µA
V
PG
PGOOD Trip Level V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Negative (UV)
V
FB
Ramping Positive (OV)
–12.5
7.5
–10
10
–7.5
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.
