LTC2965
11
2965fb
For more information www.linear.com/LTC2965
V
IN
V
IN
LTC2965
GND
REF
1µF
INH
INL
2965 F04
LT6656-2.048
OUT
R2
200k
0.1%
R1
1.8M
0.1%
R3
47.5k
0.1%
R4
10k
IN
GND
Figure 4. Reducing V
IN
Threshold Error
applicaTions inForMaTion
Output Configuration with Polarity Selection
The OUT pin may be used with a wide range of user-defined
voltages up to 100V with an external resistor. Select a
resistor compatible with desired output rise time and load
current specifications. When the status outputs are low,
power is dissipated in the pull-up resistors. An internal
pull-up is present if the OUT pins are left floating or if
low power consumption is required. The internal pull-up
resistor does not draw current if an external resistor pulls
OUT up to a voltage greater than V
OH
.
If PS is connected to ground, the comparator output is
noninverting. This means that OUT pulls low when V
IN
falls below the scaled INL voltages. OUT is released after
V
IN
rises above the scaled INH voltage. Likewise, if PS is
connected up to REF or a voltage > V
TH
, the comparator
output is inverting. This means that OUT pulls low when
V
IN
rises above the scaled INH voltage and is released
when V
IN
falls below the scaled INL voltage.
If the V
IN
pin falls below the UVLO threshold minus
hysteresis, the output is pulled to ground. The output is
guaranteed to stay low for V
IN
≥ 1.25V regardless of the
output logic configuration.
It is recommended that circuit board traces associated
with the OUT pin be located on a different layer than those
associated with the INH/INL and REF pins where possible
to avoid capacitive coupling.
Hot Swap™ Events
The LTC2965 can withstand high voltage transients up
to 140V. However, when a supply voltage is abruptly
connected to the input resonant ringing can occur as a
result of series inductance. The peak voltage could rise
to 2x the input supply, but in practice can reach 2.5x if
a capacitor with a strong voltage coefficient is present.
Circuit board trace inductances of as little as 10nH can
produce significant ringing. Ringing beyond the absolute
maximum specification can be destructive to the part and
should be avoided whenever possible. One effective means
to eliminate ringing seen at the V
IN
pins and to protect the
part is to include a 1kΩ to 5kΩ resistance between the
monitored voltage and the V
IN
pin as shown in Figure 5.
This provides damping for the resonant circuit. If there is
a decoupling capacitor on the V
IN
pins the time constant
formed by the RC network should be considered.
Figure 5. Hot Swap Protection
High Voltage Pin Creepage/Clearance Options
Appropriate spacing between component lead traces is
critical to avoid flashover between conductors. There
are multiple industry and safety standards that have
different spacing requirements depending on factors such
as operating voltage, presence of conformal coat
, elevation,
etc. The LTC2965 is available in a 16-lead MSOP package
which offers landing clearance of at least 0.79mm (0.031in).
The package incorporates unconnected pins between all
adjacent high voltage and low voltage pins to maximize
PC board trace clearance. For voltages >30V the MSOP
should be used, otherwise the smaller or DFN is sufficient
when clearance is not an issue. For more information, refer
to the printed circuit board design standards described in
IPC2221 and UL60950.
GND
LTC2965
V
INA
/V
INB
R
S
1k
V
IN
2965 F05
