LTC6253-7

14

62537f

For more information www.linear.com/LTC6253-7

APPLICATIONS INFORMATION

Figure 2. 0.7pF Feedback Cancels Parasitic Pole

Feedback Components

When feedback resistors are used to set up gain, care

must be taken to ensure that the pole formed by the

feedback resistors and the parasitic capacitance at the

inverting input does not degrade stability. For example

if the amplifier is set up in a gain of +11 configuration

with a gain resistor of 1k and a feedback resistor of 10k,

a parasitic capacitance of 7pF (device + PC board) at the

amplifier’s inverting input will cause the part to oscillate,

due to a pole formed at 25MHz. An additional capacitor of

0.7pF across the feedback resistor as shown in Figure 2

will eliminate any ringing or oscillation. In general, if

the resistive feedback network results in a pole whose

frequency lies within the closed loop bandwidth of the

amplifier, a capacitor can be added in parallel with the

feedback resistor to introduce a zero whose frequency

is close to the frequency of the pole, improving stability.

62537 F02

1k

10k

0.7pF

Power Dissipation

The LTC6253-7 is housed in a small 10-lead MS package

and typically has a thermal resistance (

is necessary to ensure that the die’s junction temperature

sipation, PD, and thermal resistance,

The power dissipation in the IC is a function of the supply

voltage, output voltage and load resistance. For a given

supply voltage with output connected to ground or supply,

the supply current is maximum and the output voltage at

half of either supply voltage for a given load resistance.

output load current) given by:

2









2

Example: For an LTC6253-7 operating on ±2.5V supplies

and driving a 100Ω load to ground, the worst-case power

dissipation is approximately given by

If both amplifiers are loaded simultaneously then the total

power dissipation is 79.2mW.

AttheAbsoluteMaximumambientoperatingtemperature,

the junction temperature under these conditions will be:

= 125 + (0.079W • 160°C/W) = 137°C

which is less than the absolute maximum junction tem-

perature for the LTC6253-7 (150°C).

Shutdown

The LTC6253-7 has SHDN pins that can shut down the

amplifier to 42µA typical supply current. The SHDN pin

needs to be taken within 0.8V of the negative supply for

the amplifier to shut down. When left floating, the SHDN

pin is internally pulled up to the positive supply and the

amplifier remains on.