Datasheet

3
LTC3778
3778f
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 15V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
Note 2: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
as follows:
LTC3778E: T
J
= T
A
+ (P
D
• 110°C/W)
Note 3: The LTC3778 is tested in a feedback loop that adjusts V
FB
to achieve
a specified error amplifier output voltage (I
TH
).
Note 4: The LTC3778E is guaranteed to meet performance specifications from
0°C to 70°C. Specifications over the –40°C to 85°C operating temperature
range are assured by design, characterization and correlation with statistical
process controls.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RUN/SS(ON)
RUN Pin Start Threshold ● 0.8 1.5 2 V
V
RUN/SS(LE)
RUN Pin Latchoff Enable Threshold RUN/SS Pin Rising 4 4.5 V
V
RUN/SS(LT)
RUN Pin Latchoff Threshold RUN/SS Pin Falling 3.5 4.2 V
I
RUN/SS(C)
Soft-Start Charge Current –0.5 –1.2 –3 µA
I
RUN/SS(D)
Soft-Start Discharge Current 0.8 1.8 3 µA
V
IN(UVLO)
Undervoltage Lockout Threshold V
IN
Falling ● 3.4 3.9 V
V
IN(UVLOR)
Undervoltage Lockout Threshold V
IN
Rising ● 3.5 4 V
TG R
UP
TG Driver Pull-Up On Resistance TG High 2 3 Ω
TG R
DOWN
TG Driver Pull-Down On Resistance TG Low 2 3 Ω
BG R
UP
BG Driver Pull-Up On Resistance BG High 3 4 Ω
BG R
DOWN
BG Driver Pull-Down On Resistance BG Low 1 2 Ω
TG t
r
TG Rise Time C
LOAD
= 3300pF 20 ns
TG t
f
TG Fall Time C
LOAD
= 3300pF 20 ns
BG t
r
BG Rise Time C
LOAD
= 3300pF 20 ns
BG t
f
BG Fall Time C
LOAD
= 3300pF 20 ns
Internal V
CC
Regulator
V
INTVCC
Internal V
CC
Voltage 6V < V
IN
< 30V, V
EXTVCC
= 4V ● 4.7 5 5.3 V
∆V
LDO(LOADREG)
Internal V
CC
Load Regulation I
CC
= 0mA to 20mA, V
EXTVCC
= 4V –0.1 ±2%
V
EXTVCC
EXTV
CC
Switchover Voltage I
CC
= 20mA, V
EXTVCC
Rising ● 4.5 4.7 V
∆V
EXTVCC
EXTV
CC
Switch Drop Voltage I
CC
= 20mA, V
EXTVCC
= 5V 150 300 mV
∆V
EXTVCC(HYS)
EXTV
CC
Switchover Hysteresis 200 mV
PGOOD Output
∆V
FBH
PGOOD Upper Threshold V
FB
Rising 7.5 10 12.5 %
∆V
FBL
PGOOD Lower Threshold V
FB
Falling – 7.5 –10 –12.5 %
∆V
FB(HYS)
PGOOD Hysteresis V
FB
Returning 1 2.5 %
V
PGL
PGOOD Low Voltage I
PGOOD
= 5mA 0.15 0.4 V