Datasheet

3
LTC3728
3728fc
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
g
m1, 2
Transconductance Amplifier g
m
I
TH1, 2
= 1.2V; Sink/Source 5uA; (Note 3) 1.3 mmho
g
mGBW1, 2
Transconductance Amplifier GBW I
TH1, 2
= 1.2V; (Note 3) 3 MHzI
Q
Input DC Supply Current (Note 4)
Normal Mode V
IN
= 15V; EXTV
CC
Tied to V
OUT1
; V
OUT1
= 5V 450 µA
Shutdown V
RUN/SS1, 2
= 0V 20 35 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) Measured at FCB pin 4.3 4.8 V
Threshold
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 – 85 – 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 1.9 V
V
RUN/SS1, 2
LT RUN/SS Pin Latchoff Arming Threshold V
RUN/SS1,
V
RUN/SS2
Rising from 3V 3.8 4.5 V
I
SCL1, 2
RUN/SS Discharge Current Soft Short Condition V
OSENSE1, 2
= 0.5V; 0.5 2 4 µA
V
RUN/SS1, 2
= 4.5V
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 65 75 85 mV
V
OSENSE1, 2
= 0.7V,V
SENSE1
–
, 2
– = 5V ● 62 75 88 mV
TG Transition Time: (Note 5)
TG1, 2 t
r
Rise Time C
LOAD
= 3300pF 50 90 ns
TG1, 2 t
f
Fall Time C
LOAD
= 3300pF 50 90 ns
BG Transition Time: (Note 5)
BG1, 2 t
r
Rise Time C
LOAD
= 3300pF 40 90 ns
BG1, 2 t
f
Fall Time C
LOAD
= 3300pF 40 80 ns
TG/BG t
1D
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time C
LOAD
= 3300pF Each Driver 90 ns
BG/TG t
2D
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time C
LOAD
= 3300pF Each Driver 90 ns
t
ON(MIN)
Minimum On-Time Tested with a Square Wave (Note 6) 100 ns
INTV
CC
Linear Regulator
V
INTVCC
Internal V
CC
Voltage 6V < V
IN
< 30V, V
EXTVCC
= 4V 4.8 5.0 5.2 V
V
LDO
INT INTV
CC
Load Regulation I
CC
= 0 to 20mA, V
EXTVCC
= 4V 0.2 1.0 %
V
LDO
EXT EXTV
CC
Voltage Drop I
CC
= 20mA, V
EXTVCC
= 5V 80 160 mV
V
EXTVCC
EXTV
CC
Switchover Voltage I
CC
= 20mA, EXTV
CC
Ramping Positive ● 4.5 4.7 V
V
LDOHYS
EXTV
CC
Hysteresis 0.2 V
Oscillator and Phase-Locked Loop
f
NOM
Nominal Frequency V
PLLFLTR
= 1.2V 360 400 440 kHz
f
LOW
Lowest Frequency V
PLLFLTR
= 0V 230 260 290 kHz
f
HIGH
Highest Frequency V
PLLFLTR
≥ 2.4V 480 550 590 kHz
R
PLLIN
PLLIN Input Resistance 50 kΩ
I
PLLFLTR
Phase Detector Output Current
Sinking Capability f
PLLIN
< f
OSC
–15 µA
Sourcing Capability f
PLLIN
> f
OSC
15 µA
The ● 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.
ELECTRICAL CHARACTERISTICS