Datasheet

LTC3859
4
3859fa
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating junction
temperature range, otherwise specifi cations are at T
A
= 25°C. V
BIAS
= 12V, V
RUN1,2,3
= 5V, EXTV
CC
= 0V unless otherwise noted. (Note 2)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
UVLO Undervoltage Lockout INTV
CC
Ramping Up
l
4.15 4.5 V
INTV
CC
Ramping Down
l
3.5 3.8 4.0 V
V
OVL1,2
Buck Feedback Overvoltage Protection Measured at V
FB1,2
Relative to
Regulated V
FB1,2
71013 %
I
SENSE1,2
+ SENSE
+
Pin Current Bucks (Channels 1 and 2) ±1 µA
I
SENSE3
+ SENSE
+
Pin Current Boost (Channel 3) 170 µA
I
SENSE1,2
– SENSE
–
Pin Current Bucks (Channels 1 and 2)
V
OUT1,2
< V
INTVCC
– 0.5V
V
OUT1,2
> V
INTVCC
+ 0.5V 700
±2 µA
µA
I
SENSE3
– SENSE
–
Pin Current Boost (Channel 3)
V
SENSE3
+, V
SENSE3
– = 12V
±1 µA
DF
MAX,TG
Maximum Duty Factor for TG Bucks (Channels 1,2) in Dropout, FREQ = 0V
Boost (Channel 3) in Overvoltage
98 99
100
%
%
DF
MAX,BG
Maximum Duty Factor for BG Bucks (Channels 1,2) in Overvoltage
Boost (Channel 3)
100
96
%
%
I
TRACK/SS1,2
Soft-Start Charge Current V
TRACK/SS1,2
= 0V 0.7 1.0 1.4 µA
I
SS3
Soft-Start Charge Current V
SS3
= 0V 0.7 1.0 1.4 µA
V
RUN1
ON
V
RUN2,3
ON
RUN1 Pin Threshold
RUN2,3 Pin Threshold
V
RUN1
Rising
V
RUN2,3
Rising
l
l
1.19
1.23
1.25
1.28
1.31
1.33
V
V
V
RUN1,2,3
Hyst RUN Pin Hysteresis 80 mV
V
SENSE1,2,3(MAX)
Maximum Current Sense Threshold V
FB1,2
= 0.7V, V
SENSE1,2
– = 3.3V
V
FB1,2,3
= 1.1V, V
SENSE3
+ = 12V
l
43 50 57 mV
V
SENSE3(CM)
SENSE3 Pins Common Mode Range
(BOOST Converter Input Supply Voltage)
2.5 38 V
Gate Driver
TG1,2 Pull-Up On-Resistance
Pull-Down On-Resistance
2.5
1.5
Ω
Ω
BG1,2 Pull-Up On-Resistance
Pull-Down On-Resistance
2.4
1.1
Ω
Ω
TG3 Pull-Up On-Resistance
Pull-Down On-Resistance
1.2
1.0
Ω
Ω
BG3 Pull-Up On-Resistance
Pull-Down On-Resistance
1.2
1.0
Ω
Ω
TG1,2,3 t
r
TG1,2,3 t
f
TG Transition Time:
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
25
16
ns
ns
BG1,2,3 t
r
BG1,2,3 t
f
BG Transition Time:
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
28
13
ns
ns
TG/BG t
1D
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
C
LOAD
= 3300pF Each Driver Bucks (Channels 1, 2)
Boost (Channel 3)
30
70
ns
ns
BG/TG t
1D
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
C
LOAD
= 3300pF Each Driver Bucks (Channels 1, 2)
Boost (Channel 3)
30
70
ns
ns
t
ON(MIN)1,2
Buck Minimum On-Time (Note 7) 95 ns
t
ON(MIN)3
Boost Minimum On-Time (Note 7) 120 ns