LT8705
6
8705ff
For more information www.linear.com/LT8705
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: Do not force voltage on the V
C
pin.
Note 3: The LT8705E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT8705I is guaranteed over the full –40°C to 125°C junction temperature
range. The LT8705H is guaranteed over the full –40°C to 150°C operating
junction temperature range. The LT8705MP is guaranteed over the full
–55°C to 150°C operating junction temperature range. Operating lifetime is
derated at junction temperatures greater than 125°C.
Note 4: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 5: This specification not applicable in the FE38 package.
Note 6: Do not apply a voltage or current source to these pins. They must
be connected to capacitive loads only, otherwise permanent damage may
occur.
Note 7: Negative voltages on the SW1 and SW2 pins are limited, in an
application, by the body diodes of the external NMOS devices, M2 and
M3, or parallel Schottky diodes when present. The SW1 and SW2 pins
are tolerant of these negative voltages in excess of one diode drop below
ground, guaranteed by design.
Note 8:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature protection is active. Continuous operation above
the specified maximum operating junction temperature may impair device
reliability.
PARAMETER CONDITIONS MIN TYP MAX UNITS
BG2 Off to TG2 On Delay C
LOAD
= 3300pF Each Driver 80 ns
Minimum On-Time for Main Switch in Boost Operation
(t
ON(M3,MIN)
)
Switch M3, C
LOAD
= 3300pF 265 ns
Minimum On-Time for Synchronous Switch in Buck
Operation (t
ON(M2,MIN)
)
Switch M2, C
LOAD
= 3300pF 260 ns
Minimum Off-Time for Main Switch in Steady-State Boost
Operation
Switch M3, C
LOAD
= 3300pF 245 ns
Minimum Off-Time for Synchronous Switch in
Steady-State Buck Operation
Switch M2, C
LOAD
= 3300pF 245 ns
Oscillator
Switch Frequency Range SYNCing or Free Running 100 400 kHz
Switching Frequency, f
OSC
R
T
= 365k
R
T
= 215k
R
T
= 124K
l
l
l
102
170
310
120
202
350
142
235
400
kHz
kHz
kHz
SYNC High Level for Synchronization
l
1.3 V
SYNC Low Level for Synchronization
l
0.5 V
SYNC Clock Pulse Duty Cycle V
SYNC
= 0V to 2V 20 80 %
Recommended Minimum SYNC Ratio f
SYNC
/f
OSC
3/4
CLKOUT Output Voltage High 1mA Out of CLKOUT Pin 2.3 2.45 2.55 V
CLKOUT Output Voltage Low 1mA Into CLKOUT Pin 25 100 mV
CLKOUT Duty Cycle T
J
= –40°C
T
J
= 25°C
T
J
= 125°C
22.7
44.1
77
%
%
%
CLKOUT Rise Time C
LOAD
= 200pF 30 ns
CLKOUT Fall Time C
LOAD
= 200pF 25 ns
CLKOUT Phase Delay SYNC Rising to CLKOUT Rising, f
OSC
= 100kHz
l
160 180 200 Deg
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
= 12V, SHDN = 3V unless otherwise noted. (Note 3)
