LTC2057 datasheet(22/32 Pages) LINER

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LTC2057/LTC2057HV

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

powerdissipationintheamplifier.Whendrivingheavyloads

at high voltages, use the

θJA 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

Tables 1 and 2.

Table 1. Shutdown Control Logic

SHUTDOWN PIN CONDITION

AMPLIFIER STATE

SD = Float, SDCOM = Float

SD – SDCOM > 2V

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

V–

V+

If the shutdown feature is not required, SD and SDCOM

may be left floating. Internal circuitry 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

–

RIN LIMITS IOVERLOAD TO <10mA

FOR VIN < 10V OUTSIDE OF THE SUPPLY RAILS.

OUT

LTC2057

VIN

V+

V–

RIN

IOVERLOAD

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