Datasheet
LTC3728L/LTC3728LX
4
3728lxff
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/SS1, 2
= 5V unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loops
V
OSENSE1, 2
Regulated Feedback Voltage (Note 3); I
TH1, 2
Voltage = 1.2V (LTC3728LC)
(Note 3); I
TH1, 2
Voltage = 1.2V
(LTC3728LE/LTC3728LX/LTC3728LI)
●
●
0.792
0.788
0.800
0.800
0.808
0.812
V
V
I
VOSENSE1, 2
Feedback Current (Note 3) –5 –50 nA
V
REFLNREG
Reference Voltage Line Regulation V
IN
= 3.6V to 30V (Note 3) 0.002 0.02 %/V
V
LOADREG
Output Voltage Load Regulation (Note 3)
Measured in Servo Loop; ΔI
TH
Voltage = 1.2V to 0.7V
Measured in Servo Loop; ΔI
TH
Voltage = 1.2V to 2.0V
●
●
0.1
–0.1
0.5
–0.5
%
%
g
m1, 2
Transconductance Amplifier g
m
I
TH1, 2
= 1.2V; Sink/Source 5µA (Note 3) 1.3 mmho
g
mGBW1, 2
Transconductance Amplifier GBW I
TH1, 2
= 1.2V (Note 8) 3 MHz
I
Q
Input DC Supply Current
Normal Mode
Shutdown
(Note 4)
V
IN
= 15V; EXTV
CC
Tied to V
OUT1
; V
OUT1
= 5V
V
RUN/SS1, 2
= 0V
450
20
35
µA
µA
V
FCB
Forced Continuous Threshold
●
0.76 0.800 0.84 V
I
FCB
Forced Continuous Pin Current V
FCB
= 0.85V –0.50 –0.18 –0.1 µA
V
BINHIBIT
Burst Inhibit (Constant-Frequency)
Threshold
Measured at FCB Pin 4.3 4.8 V
UVLO Undervoltage Lockout V
IN
Ramping Down
●
3.5 4 V
V
OVL
Feedback Overvoltage Lockout Measured at V
OSENSE1, 2
●
0.84 0.86 0.88 V
I
SENSE
Sense Pins Total Source Current (Each Channel); V
SENSE1
–
, 2
–
= V
SENSE1
+
, 2
+
= 0V –90 –60 µA
DF
MAX
Maximum Duty Factor In Dropout 98 99.4 %
I
RUN/SS1, 2
Soft-Start Charge Current V
RUN/SS1, 2
= 1.9V 0.5 1.2 µA
V
RUN/SS1, 2
ON RUN/SS Pin ON Threshold V
RUN/SS1,
V
RUN/SS2
Rising 1.0 1.5 2.0 V
V
RUN/SS1, 2
LT RUN/SS Pin Latchoff Arming
Threshold
V
RUN/SS1,
V
RUN/SS2
Rising from 3V 4.1 4.75 V
I
SCL1, 2
RUN/SS Discharge Current Soft-Short Condition V
OSENSE1, 2
= 0.5V;
V
RUN/SS1, 2
= 4.5V
0.5 2 4 µA
I
SDLHO
Shutdown Latch Disable Current V
OSENSE1, 2
= 0.5V 1.6 5 µA
V
SENSE(MAX)
Maximum Current Sense Threshold V
OSENSE1, 2
= 0.7V, V
SENSE1
–
, 2
– = 5V
V
OSENSE1, 2
= 0.7V, V
SENSE1
–
, 2
– = 5V
●
65
62
75
75
85
88
mV
mV
TG1, 2 t
r
TG1, 2 t
f
TG Transition Time:
Rise Time
Fall Time
(Note 5)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
55
55
100
100
ns
ns
BG1, 2 t
r
BG1, 2 t
f
BG Transition Time:
Rise Time
Fall Time
(Note 5)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
45
45
100
90
ns
ns
TG/BG t
1D
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
C
LOAD
= 3300pF Each Driver
80
ns
BG/TG t
2D
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
C
LOAD
= 3300pF Each Driver
80
ns
t
ON(MIN)
Minimum On-Time Tested with a Square Wave (Note 6) 100 ns