Datasheet

LTC2057/LTC2057HV
22
2057f
For more information www.linear.com/LTC2057
applicaTions inForMaTion
Power Dissipation
Since the LTC2057/LTC2057HV is capable of operating at
>30V total supply, care should be taken with respect to
power dissipation in the amplifier. When driving heavy loads
at high voltages, use the θ
JA
of the package to estimate
the resulting die-temperature rise and take measures to
ensure that the resulting junction temperature does not
exceed specified limits. PCB metallization and heat sinking
should also be considered when high power dissipation
is expected. Thermal information for all packages can be
found in the Pin Configuration section.
Electrical Overstress
Absolute Maximum Ratings should not be exceeded.
Avoid driving the input and output pins beyond the rails,
especially at supply voltages approaching 60V. If these
fault conditions cannot be prevented, a series resistor at
the pin of interest should help to limit the input current and
reduce the possibility of device damage. This technique
is shown in Figure 8.
Keep the value of the current limiting resistance as low
as possible to avoid adding noise and error voltages from
interaction with input bias currents but high enough to
protect the device. Resistances up to 2k will not seriously
impact noise or precision.
Shutdown Mode
The LTC2057/
LTC2057HV features a shutdown mode for
low-power applications. In the OFF state, the amplifier
draws less than 11μA of supply current under all normal
operating conditions, and the output presents a high-
impedance to external circuitry.
Shutdown control is accomplished through differential
signaling. This method allows for low voltage digital
control logic to operate independently of the amplifier’s
high voltage supply rails.
Shutdown operation is accomplished by tying SDCOM to
logic ground and SD to a 3V or 5V logic signal. A sum
-
mary of
control logic and operating ranges is shown in
T
ables 1 and 2.
Table 1. Shutdown Control Logic
SHUTDOWN PIN CONDITION AMPLIFIER STATE
SD = Float, SDCOM = Float ON
SD – SDCOM > 2V ON
SD – SDCOM < 0.8V OFF
Table 2. Operating Voltage Range for Shutdown Pins
MIN MAX
SD – SDCOM –0.2V 5.2V
SDCOM V
–
V
+
–2V
SD V
–
V
+
If the shutdown feature is not required, SD and SDCOM
may be left floating. Internal cir
cuitry will automatically
keep the amplifier in the ON state.
For operation in noisy environments, a capacitor between
SD and SDCOM is recommended to prevent noise from
changing the shutdown state.
When there is a danger of SD and SDCOM being pulled
beyond the supply rails, resistance in series with the shut
-
down pins
is recommended to limit the resulting current.
Figure 8. Using a Resistor to Limit Input Current
2057 F08
+
–
R
IN
LIMITS I
OVERLOAD
TO <10mA
FOR V
IN
< 10V OUTSIDE OF THE SUPPLY RAILS.
OUTLTC2057
V
IN
V
+
V
–
R
IN
1k
I
OVERLOAD