D1

D2

D3

D4

NON-INVERTING

INPUT

INVERTING

INPUT

RS

200-400:

13

LMV116, LMV118

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SNOSA87C – OCTOBER 2003 – REVISED OCTOBER 2016

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7.4 Device Functional Modes

7.4.1 Quasi-Saturated State

When the output swing approaches either supply rail, the output transistor enters a quasi-saturated state. A

subtle effect of this operational region is that there is an increase in supply current in this state (up to 1 mA). The

onset of quasi-saturation region is a function of output loading (current) and varies from 100 mV at no load to

about 1 V when output is delivering 20 mA, as measured from supplies. Both input common mode voltage and

output voltage level affect the supply current (see Typical Characteristics for plot).

7.4.2 Micro-Power Shutdown

The LMV118 can be shut down to save power and reduce its supply current to less than the 50 μA specified by

applying a voltage to the SD pin. The SD pin is active high and needs to be tied to V− for normal operation. This

input is low current (< 20-μA, 4-pF equivalent capacitance) and a resistor to V

− (≤ 20 kΩ) results in normal

operation. Shutdown is specified when SD pin is 0.4 V or less from V+ at any operating supply voltage and

temperature.

In the shutdown mode, essentially all internal device biasing is turned off in order to minimize supply current flow,

and the output goes into Hi-Z (high impedance) mode. Complete device turnon and turnoff times vary

considerably relative to the output loading conditions, output voltage, and input impedance, but is generally

limited to less than 1 μs (see Electrical Characteristics: 2.7 V, Electrical Characteristics: 5 V, and Electrical

Characteristics: ±5 V)

During shutdown, the input stage has an equivalent circuit as shown in Figure 20.

Figure 20. Input Stage Shutdown Equivalent Circuit

As can be seen from Figure 20, in shutdown there may be current flow through the internal diodes shown,

caused by input potential, if present. This current may flow through the external feedback resistor and result in an

apparent output signal. In most shutdown applications the presence of this output is inconsequential. However, if

the output is forced by another device such as in a multiplexer, the other device must conduct the current

described in order to maintain the output potential.

To keep the output at or near ground during shutdown when there is no other device to hold the output low, a

switch (transistor) could be used to shunt the output to ground. Figure 21 shows a circuit where a NPN bipolar is

used to keep the output near ground (approximately 80 mV):