Datasheet LT1210X (Analog Devices) - 9
| Fabricante | Analog Devices |
| Descripción | High Temperature 1.0A, 35MHz Current Feedback Amplifier |
| Páginas / Página | 18 / 9 — Figure 2. Shutdown Interface. Figure 1. Shutdown/Current Set. If the … |
| Formato / tamaño de archivo | PDF / 635 Kb |
| Idioma del documento | Inglés |
Figure 2. Shutdown Interface. Figure 1. Shutdown/Current Set. If the shutdown feature is not used, the SHUTDOWN pin
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LT1210X APPLICATIONS INFORMATION Although the optional compensation works well with 15V capacitive loads, it simply reduces the bandwidth when VIN + it is connected with resistive loads. For instance, with a LT1210X V 10Ω load, the bandwidth drops from 35MHz to 26MHz OUT –SD when the compensation is connected. Hence, the com- RF –15V pensation was made optional. To disconnect the optional compensation, leave the COMP pin open. 5V 74C906 24kΩ RG ENABLE 15V 14 12 VS = ±15V CL = 200pF RF = 3.4kΩ 1210X F02 10 NO COMPENSATION
Figure 2. Shutdown Interface
8 RF = 1.5kΩ COMPENSATION 6 4 2 VOLTAGE GAIN (dB) 0 –2 VOUT –4 RF = 3.4kΩ COMPENSATION –6 1 10 100 FREQUENCY (MHz) ENABLE 1210X F01
Figure 1 Shutdown/Current Set
A 1210X F03 V = 1 RPULL-UP = 24kΩ RF = 825Ω VIN = 1VP-P
If the shutdown feature is not used, the SHUTDOWN pin
RL = 50Ω VS = ±15V
must be connected to ground or V–. Figure 3. Shutdown Operation
The Shutdown pin can be used to either turn off the bias- ing for the amplifier, reducing the quiescent current to have a breakdown voltage of greater than the positive less than 200µA, or to control the quiescent current in supply voltage. No other circuitry is necessary as the normal operation. internal circuit limits the Shutdown pin current to about 500µA. Figure 3 shows the resulting waveforms. The total bias current in the LT1210X is controlled by the current flowing out of the Shutdown pin. When the For applications where the full bandwidth of the amplifier Shutdown pin is open or driven to the positive supply, is not required, the quiescent current of the device may be the part is shut down. In the shutdown mode, the output reduced by connecting a resistor from the Shutdown pin looks like a 70pF capacitor and the supply current is typi- to ground. The quiescent current will be approximately 65 cally less than 100µA. The Shutdown pin is referenced to times the current in the Shutdown pin. The voltage across the positive supply through an internal bias circuit (see the resistor in this condition is V+ – 3VBE. For example, the Simplified Schematic). An easy way to force shutdown a 82kΩ resistor will set the quiescent supply current to is to use open-drain (collector) logic. The circuit shown 9mA with VS = ±15V. in Figure 2 uses a 74C906 buffer to interface between 5V The photos in Figures 4a and 4b show the effect of reduc- logic and the LT1210X. The switching time between the ing the quiescent supply current on the large-signal active and shutdown states is about 1µs. A 24kΩ pull-up response. The quiescent current can be reduced to 9mA resistor speeds up the turn-off time and ensures that the in the inverting configuration without much change in LT1210X is completely turned off. Because the pin is response. In noninverting mode, however, the slew rate referenced to the positive supply, the logic used should is reduced as the quiescent current is reduced. 1210Xfa For more information www.linear.com/LT1210X 9
Figure 2. Shutdown Interface
8 RF = 1.5kΩ COMPENSATION 6 4 2 VOLTAGE GAIN (dB) 0 –2 VOUT –4 RF = 3.4kΩ COMPENSATION –6 1 10 100 FREQUENCY (MHz) ENABLE 1210X F01
Figure 1 Shutdown/Current Set
A 1210X F03 V = 1 RPULL-UP = 24kΩ RF = 825Ω VIN = 1VP-P
If the shutdown feature is not used, the SHUTDOWN pin
RL = 50Ω VS = ±15V
must be connected to ground or V–. Figure 3. Shutdown Operation
The Shutdown pin can be used to either turn off the bias- ing for the amplifier, reducing the quiescent current to have a breakdown voltage of greater than the positive less than 200µA, or to control the quiescent current in supply voltage. No other circuitry is necessary as the normal operation. internal circuit limits the Shutdown pin current to about 500µA. Figure 3 shows the resulting waveforms. The total bias current in the LT1210X is controlled by the current flowing out of the Shutdown pin. When the For applications where the full bandwidth of the amplifier Shutdown pin is open or driven to the positive supply, is not required, the quiescent current of the device may be the part is shut down. In the shutdown mode, the output reduced by connecting a resistor from the Shutdown pin looks like a 70pF capacitor and the supply current is typi- to ground. The quiescent current will be approximately 65 cally less than 100µA. The Shutdown pin is referenced to times the current in the Shutdown pin. The voltage across the positive supply through an internal bias circuit (see the resistor in this condition is V+ – 3VBE. For example, the Simplified Schematic). An easy way to force shutdown a 82kΩ resistor will set the quiescent supply current to is to use open-drain (collector) logic. The circuit shown 9mA with VS = ±15V. in Figure 2 uses a 74C906 buffer to interface between 5V The photos in Figures 4a and 4b show the effect of reduc- logic and the LT1210X. The switching time between the ing the quiescent supply current on the large-signal active and shutdown states is about 1µs. A 24kΩ pull-up response. The quiescent current can be reduced to 9mA resistor speeds up the turn-off time and ensures that the in the inverting configuration without much change in LT1210X is completely turned off. Because the pin is response. In noninverting mode, however, the slew rate referenced to the positive supply, the logic used should is reduced as the quiescent current is reduced. 1210Xfa For more information www.linear.com/LT1210X 9