Datasheet

LTC3780
4
3780ff
For more information www.linear.com/LTC3780
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. (Note 7) V
IN
= 15V unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
DF MAX, Boost Maximum Duty Factor % Switch C On 99 %
DF MAX, Buck Maximum Duty Factor % Switch A On (in Dropout) 99 %
V
RUN(ON)
RUN Pin On Threshold V
RUN
Rising 1 1.5 2 V
I
SS
Soft-Start Charge Current V
RUN
= 2V 0.5 1.2 µA
V
SENSE(MAX)
Maximum Current Sense Threshold Boost: V
OSENSE
= V
REF
– 50mV
Buck: V
OSENSE
= V
REF
– 50mV
l
l
120
–95
160
–110
185
–150
mV
mV
V
SENSE(MIN,BUCK)
Minimum Current Sense Threshold Discontinuous Mode –6 mV
TG1, TG2 t
r
TG Rise Time C
LOAD
= 3300pF (Note 5) 50 ns
TG1, TG2 t
f
TG Fall Time C
LOAD
= 3300pF (Note 5) 45 ns
BG1, BG2 t
r
BG Rise Time C
LOAD
= 3300pF (Note 5) 45 ns
BG1, BG2 t
f
BG Fall Time C
LOAD
= 3300pF (Note 5) 55 ns
TG1/BG1 t
1D
TG1 Off to BG1 On Delay,
Switch C On Delay
C
LOAD
= 3300pF Each Driver 80 ns
BG1/TG1 t
2D
BG1 Off to TG1 On Delay,
Synchronous Switch D On Delay
C
LOAD
= 3300pF Each Driver 80 ns
TG2/BG2 t
3D
TG2 Off to BG2 On Delay,
Synchronous Switch B On Delay
C
LOAD
= 3300pF Each Driver 80 ns
BG2/TG2 t
4D
BG2 Off to TG2 On Delay,
Switch A On Delay
C
LOAD
= 3300pF Each Driver 80 ns
Mode
Transition 1
BG1 Off to BG2 On Delay,
Switch A On Delay
C
LOAD
= 3300pF Each Driver 250 ns
Mode
Transition 2
BG2 Off to BG1 On Delay,
Synchronous Switch D On Delay
C
LOAD
= 3300pF Each Driver 250 ns
t
ON(MIN,BOOST)
Minimum On-Time for Main Switch in
Boost Operation
Switch C (Note 6) 200 ns
t
ON(MIN,BUCK)
Minimum On-Time for Synchronous
Switch in Buck Operation
Switch B (Note 6) 180 ns
Internal V
CC
Regulator
V
INTVCC
Internal V
CC
Voltage 7V < V
IN
< 30V, V
EXTVCC
= 5V
l
5.7 6 6.3 V
∆V
LDO(LOADREG)
Internal V
CC
Load Regulation I
CC
= 0mA to 20mA, V
EXTVCC
= 5V 0.2 2 %
V
EXTVCC
EXTV
CC
Switchover Voltage I
CC
= 20mA, V
EXTVCC
Rising
l
5.4 5.7 V
∆V
EXTVCC(HYS)
EXTV
CC
Switchover Hysteresis 300 mV
∆V
EXTVCC
EXTV
CC
Switch Drop Voltage I
CC
= 20mA, V
EXTVCC
= 6V 150 300 mV
Oscillator and Phase-Locked Loop
f
NOM
Nominal Frequency V
PLLFLTR
= 1.2V 260 300 330 kHz
f
LOW
Lowest Frequency V
PLLFLTR
= 0V 170 200 220 kHz
f
HIGH
Highest Frequency V
PLLFLTR
= 2.4V 340 400 440 kHz
R
PLLIN
PLLIN Input Resistance 50 kΩ
I
PLLLPF
Phase Detector Output Current f
PLLIN
< f
OSC
f
PLLIN
> f
OSC
(Note 9)
–15
15
µA
µA