Datasheet
LTC3855
3
3855f
orDer inForMaTion
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3855EFE#PBF LTC3855EFE#TRPBF LTC3855FE 38-Lead Plastic TSSOP –40°C to 85°C
LTC3855IFE#PBF LTC3855IFE#TRPBF LTC3855FE 38-Lead Plastic TSSOP –40°C to 125°C
LTC3855EUJ#PBF LTC3855EUJ#TRPBF LTC3855UJ
40-Lead (6mm × 6mm) Plastic QFN
–40°C to 85°C
LTC3855IUJ#PBF LTC3855IUJ#TRPBF LTC3855UJ
40-Lead (6mm × 6mm) Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loops
V
IN
Input Voltage Range 4.5 38 V
V
OUT
Output Voltage Range 0.6 12.5 V
V
FB1,2
Regulated Feedback Voltage I
TH1,2
Voltage = 1.2V (Note 4)
I
TH1,2
Voltage = 1.2V (Note 4), T
A
= 125°C
l
l
0.5955
0.594
0.600
0.600
0.6045
0.606
V
V
I
FB1,2
Feedback Current (Note 4) –15 –50 nA
V
REFLNREG
Reference Voltage Line Regulation V
IN
= 4.5V to 38V (Note 4) 0.002 0.02 %/V
V
LOADREG
Output Voltage Load Regulation (Note 4)
Measured in Servo Loop; ∆I
TH
Voltage = 1.2V to 0.7V
Measured in Servo Loop; ∆I
TH
Voltage = 1.2V to 1.6V
l
l
0.01
–0.01
0.1
–0.1
%
%
g
m1,2
Transconductance Amplifier g
m
I
TH1,2
= 1.2V; Sink/Source 5µA; (Note 4) 2 mmho
I
Q
Input DC Supply Current
Normal Mode
Shutdown
(Note 5)
V
IN
= 15V
V
RUN1,2
= 0V
3.5
30
50
mA
µA
DF
MAX
Maximum Duty Factor In Dropout, f
OSC
= 500kHz 94 95 %
UVLO Undervoltage Lockout V
INTVCC
Ramping Down
l
3.0 3.2 3.4 V
UVLO
HYS
UVLO Hysteresis 0.6 V
V
OVL1,2
Feedback Overvoltage Lockout Measured at V
FB1,2
l
0.64 0.66 0.68 V
I
SENSE1,2
Sense Pins Bias Current (Each Channel); V
SENSE1,2
= 3.3V
l
±1 ±2 µA
I
TEMP1,2
DCR Tempco Compensation Current V
ITEMP1,2
= 0.2V
l
9 10 11 µA
I
TK/SS1,2
Soft-Start Charge Current V
TK/SS1,2
= 0V
l
1 1.2 1.4 µA
V
RUN1,2
RUN Pin ON Threshold V
RUN1
, V
RUN2
Rising
l
1.1 1.22 1.35 V
V
RUN1,2HYS
RUN Pin ON Hysteresis 80 mV
V
SENSE(MAX)
Maximum Current Sense Threshold V
FB1,2
= 0.5V, V
SENSE1,2
= 3.3V, I
LIM
= 0V
V
FB1,2
= 0.5V, V
SENSE1,2
= 3.3V, I
LIM
= Float
V
FB1,2
= 0.5V, V
SENSE1,2
= 3.3V, I
LIM
= INTV
CC
l
l
l
25
45
68
30
50
75
35
55
82
mV
mV
mV
TG1, 2 t
r
TG1, 2 t
f
TG Transition Time:
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
25
25
ns
ns
BG1, 2 t
r
BG1, 2 t
f
BG Transition Time:
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
25
25
ns
ns
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
junction temperature range (E-Grade), otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN1,2
= 5V unless otherwise noted.