Datasheet

LTC3854
3
3854fb
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, V
RUN
= 5V, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loop
V
IN
Operating Input Voltage Range 4.5 38 V
V
FB
Regulated Feedback Voltage (Note 4); ITH Voltage = 1.2V l 0.792 0.8 0.808 V
I
FB
Feedback Current (Note 4) ±5 ±50 nA
V
REFLNREG
Reference Voltage Line Regulation V
IN
= 6V to 38V (Note 4) 0.002 0.02 %/V
V
LOADREG
Output Voltage Load Regulation (Note 4) Measured in Servo Loop;
∆
ITH
Voltage = 0.7V to 1.2V
Measured in Servo Loop;
∆
ITH
Voltage = 1.2V to 2V
l
l
0.1
–0.1
0.5
–0.5
%
%
gm Transconductance Amplifier gm ITH = 1.2V; Sink/Source = 5µA (Note 4) 2.0 mmho
gm
GBW
Transconductance Amplifier GBW ITH = 1.2V; (Guaranteed by Design) 3 MHz
I
Q
Input DC Supply Current
Normal Mode
Shutdown
(Note 5)
RUN = 0V
2
10
3
25
mA
µA
UVLO Undervoltage Lockout V
IN
Ramping Down; Measured at INTV
CC
l 3.0 3.5 V
UVLO
HYST
Undervoltage Lockout Hysteresis V
IN
Ramping Down then Up; Measured at INTV
CC
350 mV
V
OVL
Feedback Overvoltage Lockout Measured at FB l 0.86 0.88 0.90 V
I
SENSE
Sense Pins Source Current V
SENSE
– = V
SENSE
+ = 3.3V ±0.5 ±1 µA
DF
MAX
Maximum Duty Factor In Dropout 97 98 %
I
RUN/SS
Soft-Start Charge Current RUN/SS = 0V 0.6 1.25 2.0 µA
V
RUN/SS_SD
Shutdown Threshold RUN/SS Pin Must be Taken Below this Value to
Reset Part (or Put into Shutdown Mode)
0.4 V
V
RUN/SS_ON
Soft-Start Threshold Soft-Start Mode 1.2 V
V
SENSE(MAX)
Maximum Current Sense Threshold FB = 0.7V, V
SENSE
– = 3.3V, V
IN
= 6V 40 50 65 mV
TG R
UP
TG Driver Pull-Up On Resistance TG High 2.5 Ω
TG R
DOWN
TG Driver Pull-Down On Resistance TG Low 2.1 Ω
BG R
UP
BG Driver Pull-Up On Resistance BG High 2.5 Ω
BG R
DOWN
BG Driver Pull-down On Resistance BG Low 1.2 Ω
TG t
r
TG t
f
TG Transition Time:
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
25
25
ns
ns
BG t
r
BG t
f
BG Transition Time:
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
25
25
ns
ns
TG/BG t
1D
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
C
LOAD
= 3300pF Each Driver 30 ns
BG/TG t
2D
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
C
LOAD
= 3300pF Each Driver 30 ns
t
ON(MIN)
Minimum On-Time (Note 7) 75 ns
INTV
CC
Linear Regulator
V
INTVCC
Internal V
CC
Voltage 6V < V
IN
< 38V 4.8 5.0 5.2 V
V
LDO
INT INTV
CC
Load Regulation I
CC
= 0 to 20mA 0.2 1.0 %
Oscillator
f
SW
Switching Frequency 360 400 440 kHz