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ELECTRICAL CHARACTERISTICS
junction temperature range, otherwise specifications are at T
PARAMETER
NMOS Gate Drivers
TG1, TG2 Rise Time
TG1, TG2 Fall Time
BG1, BG2 Rise Time
BG1, BG2 Fall Time
TG1 Off to BG1 On Delay
BG1 Off to TG1 On Delay
TG2 Off to BG2 On Delay
BG2 Off to TG2 On Delay
Min On-Time for Main Switch in Boost Operation (t
Min On-Time for Synchronous Switch in Buck Operation (t
Min Off-Time for Main Switch in Steady-State Boost Operation
Min Off-Time for Synchronous Switch in Steady-State Buck Operation Switch M2, C
Oscillator
Switch Frequency Range
Switching Frequency, f
OSC
SYNC High Level for Synchronization
SYNC Low Level for Synchronization
SYNC Clock Pulse Duty Cycle
Recommended Min SYNC Ratio f
CLKOUT Output Voltage High
CLKOUT Output Voltage Low
CLKOUT Duty Cycle
CLKOUT Rise Time
CLKOUT Fall Time
CLKOUT Phase Delay
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
Note 3: The LT8708E-1 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 LT8708I-1 is guaranteed over the full –40°C to 125°C junction
temperature range. The LT8708H-1 is guaranteed over the full –40°C to
150°C operating junction temperature range.
Note 4: Rise and fall times are measured using 10% and 90% levels.
Delay times are measured using 50% levels.
)
ON(M3,MIN)
) Switch M2, C
ON(M2,MIN)
/f
SYNC
OSC
pin.
C
For more information
The
denotes the specifications which apply over the specified operating
l
= 25°C. V
=12V, SHDN = 3V, DIR = 3.3V unless otherwise noted. (Note 3).
A
INCHIP
CONDITIONS
C
= 3300pF (Note 4)
LOAD
C
= 3300pF (Note 4)
LOAD
C
= 3300pF (Note 4)
LOAD
C
= 3300pF (Note 4)
LOAD
C
= 3300pF Each Driver
LOAD
C
= 3300pF Each Driver
LOAD
C
= 3300pF Each Driver
LOAD
C
= 3300pF Each Driver
LOAD
Switch M3, C
= 3300pF
LOAD
= 3300pF
LOAD
Switch M3, C
= 3300pF
LOAD
= 3300pF
LOAD
SYNCing or Free Running
R
= 365k
T
R
= 215k
T
R
= 124k
T
V
= 0V to 2V
SYNC
V
– V
, 1mA Out of CLKOUT Pin,
LDO33
CLKOUT
I
= 0µA
LDO33
1mA Into CLKOUT Pin
T
= –40°C
J
T
= 25°C
J
T
= 125°C
J
C
= 200pF
LOAD
C
= 200pF
LOAD
SYNC Rising to CLKOUT Rising, f
Note 5: 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 6: 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 7: 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.
Note 8: Do not force voltage or current into these pins.
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LT8708-1
MIN
TYP
20
20
20
20
90
80
90
80
200
200
230
230
100
102
120
l
170
202
l
310
350
l
1.3
l
l
20
3/4
100
25
22.7
44.1
77
20
20
= 100kHz
160
180
l
OSC
MAX
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
400
kHz
142
kHz
235
kHz
400
kHz
V
0.5
V
80
%
250
mV
100
mV
%
%
%
ns
ns
200
Degree
Rev 0
7
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