Datasheet

LTC3878
3
3878fa
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: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
as follows:
T
J
= T
A
+ (P
D
• 110°C/W)
Note 3: The LTC3878 is tested in a feedback loop that adjusts V
FB
to
achieve a specified error amplifier output voltage (I
TH
).
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
t
OFF(MIN)
Minimum Off-Time I
ON
= 30µA 220 300 ns
V
SENSE(MAX)
Valley Current Sense Threshold
V
PGND
– V
SW
Peak Current = Valley + Ripple
V
RNG
= 1V, V
FB
= 0.76V
V
RNG
= 0V, V
FB
= 0.76V
V
RNG
= INTV
CC
, V
FB
= 0.76V
l
l
l
108
74
152
133
93
186
165
119
224
mV
mV
mV
V
SENSE(MIN)
Minimum Current Sense Threshold
V
PGND
– V
SW
Forced Continuous Operation
V
RNG
= 1V, V
FB
= 0.84V
V
RNG
= 0V, V
FB
= 0.84V
V
RNG
= INTV
CC
, V
FB
= 0.84V
–67
–47
–93
mV
mV
mV
V
RUN/SS
RUN/SS Pin On Threshold V
RUN/SS
Rising 1.4 1.5 1.6 V
Soft-Start Charging Current V
RUN/SS
= 0V –1.2 µA
INTV
CC(UVLO)
INTV
CC
Undervoltage Lockout Falling
l
3.3 3.9 V
INTV
CC(UVLOR)
INTV
CC
Undervoltage Lockout Release Rising
l
3.6 4 V
TG Driver Pull-Up On-Resistance TG High 2.5 Ω
TG
Driver Pull-Down On-Resistance TG Low 1.2 Ω
BG
Driver Pull-Up On-Resistance BG High 2.5 Ω
BG
Driver Pull-Down On-Resistance BG Low 0.7 Ω
TG
Rise Time C
LOAD
= 3300pF (Note 5) 20 ns
TG Fall Time C
LOAD
= 3300pF (Note 5) 20 ns
BG Rise Time C
LOAD
= 3300pF (Note 5) 20 ns
BG Fall Time C
LOAD
= 3300pF (Note 5) 20 ns
TG/BG t
1D
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
C
LOAD
= 3300pf Each Driver (Note 5) 15 ns
TG/BG t
2D
Bottom Gate Off to Top Gate On Delay
Synchronous Switch-On Delay Time
C
LOAD
= 3300pf Each Driver (Note 5) 15 ns
Internal V
CC
Regulator
Internal V
CC
Voltage 6V < V
IN
< 38V 5.15 5.3 5.45 V
Internal V
CC
Load Regulation I
CC
= 0mA to 20mA –0.1 ±2 %
PGOOD Output
PGOOD Upper Threshold V
FB
Rising 5.5 7.5 9.5 %
PGOOD Lower Threshold V
FB
Falling –5.5 –7.5 –9.5 %
PGOOD Hysteresis V
FB
Returning 2 3.5 %
PGOOD Low Voltage I
PGOOD
= 5mA 0.15 0.4 V
PGOOD Turn-On Delay 12 µs
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V unless otherwise noted.
Note 4: The LTC3878E is guaranteed to meet specifications from
0°C to 85°C. Specifications over the –40°C to 85°C operating temperature
range are assured by design, characterization and correlation with
statistical process controls. The LTC3878I is guaranteed to meet
specifications over the full –40°C to 85°C operating temperature range.
Note 5: Rise and fall time are measured using 10% and 90% levels. Delay
times are measured using 50% levels.