LMV601_15 Datasheet, PDF (15/30 Pages) Texas Instruments – LMV601/LMV602/LMV604 1 MHz, Low Power General Purpose, 2.7V Operational Amplifiers

LMV601, LMV602, LMV604
www.ti.com
SNOSC70B – APRIL 2012 – REVISED MARCH 2013
Figure 45 shows the schematic of a simple sample and hold circuit. When the sample clock is high the first
amplifier is in normal operation mode and the second amplifier acts as a buffer. The capacitor, which appears as
a load on the first amplifier, will be charging at this time. The voltage across the capacitor is that of the non-
inverting input of the first amplifier since it is connected as a voltage-follower. When the sample clock is low the
first amplifier is shut off, bringing the output impedance to a high value. The high impedance of this output, along
with the very high impedance on the input of the second amplifier, prevents the capacitor from discharging. There
is very little voltage droop while the first amplifier is in shutdown mode. The second amplifier, which is still in
normal operation mode and is connected as a voltage follower, also provides the voltage sampled on the
capacitor at its output.
V⁺
V⁺
-
V_IN
+
-
V_OUT
+
SAMPL
E
CLOCK
C = 200pF
Figure 45. Sample and Hold Circuit
SHUTDOWN FEATURE
The LMV601 is capable of being turned off in order to conserve power and increase battery life in portable
devices. Once in shutdown mode the supply current is drastically reduced, 1µA maximum, and the output will be
"tri-stated."
The device will be disabled when the shutdown pin voltage is pulled low. The shutdown pin should never be left
unconnected. Leaving the pin floating will result in an undefined operation mode and the device may oscillate
between shutdown and active modes.
The LMV601 typically turns on 2.8µs after the shutdown voltage is pulled high. The device turns off in less than
400ns after shutdown voltage is pulled low. Figure 46 and Figure 47 show the turn-on and turn-off time of the
LMV601, respectively. In order to reduce the effect of the capacitance added to the circuit by the scope probe, in
the turn-off time circuit a resistive load of 600Ω is added. Figure 48 and Figure 49 show the test circuits used to
obtain the two plots.
V_S = 5V
TIME (400 ns/div)
Figure 46. Turn-on Time
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