LT1810CMS8#PBF Linear Technology, LT1810CMS8#PBF Datasheet - Page 18

• Manufacturer Part Number: LT1810CMS8#PBF
• Description: IC OPAMP R-R I/O DUAL 8-MSOP
• Manufacturer: Linear Technology

Specifications of LT1810CMS8#PBF

• Amplifier Type: General Purpose
• Number Of Circuits: 2
• Output Type: Rail-to-Rail
• Slew Rate: 350 V/µs
• Gain Bandwidth Product: 180MHz
• -3db Bandwidth: 320MHz
• Current - Input Bias: 12.5µA
• Voltage - Input Offset: 800µV
• Current - Supply: 15mA
• Current - Output / Channel: 85mA
• Voltage - Supply, Single/dual (±): 2.5 V ~ 12.6 V, ±1.25 V ~ 6.3 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LT1809/LT1810
The output of the amplifi er has reverse-biased diodes
connected to each supply. If the output is forced beyond
either supply, unlimited current will fl ow through these
diodes. If the current is transient and limited to several
hundred milliamps, no damage to the device will occur.
Overdrive Protection
When the input voltage exceeds the power supplies, two
pairs of crossing diodes, D1 to D4, will prevent the out-
put from reversing polarity. If the input voltage exceeds
either power supply by 700mV, diodes D1/D2 or D3/D4
will turn on, keeping the output at the proper polarity.
For the phase reversal protection to perform properly,
the input current must be limited to less than 5mA. If
the amplifi er is severely overdriven, an external resistor
should be used to limit the overdrive current.
The LT1809/LT1810’s input stages are also protected
against differential input voltages of 1.4V or higher by
back-to-back diodes, D5/D8, that prevent the emitter-
base breakdown of the input transistors. The current in
these diodes should be limited to less than 10mA when
they are active. The worst-case differential input voltage
usually occurs when the input is driven while the output
is shorted to ground in a unity-gain confi guration. In ad-
dition, the amplifi er is protected against ESD strikes up
to 3kV on all pins by a pair of protection diodes on each
pin that are connected to the power supplies as shown
in Figure 1.
Capacitive Load
The LT1809/LT1810 is optimized for high bandwidth and
low distortion applications. It can drive a capacitive load
about 20pF in a unity-gain confi guration and more with
higher gain. When driving a larger capacitive load, a resistor
18
of 10Ω to 50Ω should be connected between the output
and the capacitive load to avoid ringing or oscillation. The
feedback should still be taken from the output so that the
resistor will isolate the capacitive load to ensure stability.
Graphs on capacitive loads indicate the transient response
of the amplifi er when driving capacitive load with a speci-
fi ed series resistor.
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 total capacitance at the inverting input
does not degrade stability. For instance, the LT1809 in a
noninverting gain of 2, set up with two 1k resistors and a
capacitance of 3pF (device plus PC board), will probably
ring in transient response. The pole that is formed at
106MHz will reduce phase margin by 34 degrees when the
crossover frequency of the amplifi er is around 70MHz. A
capacitor of 3pF or higher connected across the feedback
resistor will eliminate any ringing or oscillation.
SHDN Pin
The LT1809 has a SHDN pin to reduce the supply current
to less than 1.25mA. When the SHDN pin is pulled low,
it will generate a signal to power down the device. If the
pin is left unconnected, an internal pull-up resistor of 10k
will keep the part fully operating as shown in Figure 1. The
output will be high impedance during shutdown, and the
turn-on and turn-off time is less than 100ns. Because the
inputs are protected by a pair of back-to-back diodes, the
input signal will feed through to the output during shut-
down mode if the amplitude of signal between the inputs
is larger than 1.4V.
180910fa