LMH6601_14 Datasheet, PDF (19/37 Pages) National Semiconductor (TI) – LMH6601/LMH6601Q 250 MHz, 2.4V CMOS Operational Amplifier with Shutdown

LMH6601, LMH6601-Q1
www.ti.com
SNOSAK9E – JUNE 2006 – REVISED MARCH 2013
V⁺
LMH6601 ^VO
R_P
R_L
V^-
V^-
(a) DUAL SUPPLY
R_P d RL _{¨¨©§VO}^V_{_M- IN} -1
V_{O_MIN} is the most
negative swing at output
V⁺
LMH6601 ^VO
R_P
I_L-MAX
C_O
R_L
(b) AC COUPLED LOAD
R_P d
V_{O_MIN}
I_{L_MAX}
V_{O_MIN} is the most
negative swing at output
and I_{L_MAX} is maximum load
current with direction shown
Figure 49. Output Pull-Down Value for Dual Supply & AC Coupling
Furthermore, with a combination of low closed loop gain setting (i.e. A_V = +1 for example where device
bandwidth is the highest), light output loading (R_L > 1 kΩ) , and with a significant capacitive load (C_L > 10 pF) ,
the LMH6601 is most stable if output sink current is kept to less than about 5 mA. The pull-down method
described in Figure 49 is applicable in these cases as well where the current that would normally be sunk by the
op amp is diverted to the R_P path instead.
SHUTDOWN CAPABILITY AND TURN ON/ OFF BEHAVIOR
With the device in shutdown mode, the output goes into high impedance (R_OUT > 100 MΩ) mode. In this mode,
the only path between the inputs and the output pin is through the external components around the device. So,
for applications where there is active signal connection to the inverting input, with the LMH6601 in shutdown, the
output could show signal swings due to current flow through these external components. For non-inverting
amplifiers in shutdown, no output swings would occur, because of complete input-output isolation, with the
exception of capacitive coupling.
For maximum power saving, the LMH6601 supply current drops to around 0.1 μA in shutdown. All significant
power consumption within the device is disabled for this purpose. Because of this, the LMH6601 turn on time is
measured in micro-seconds whereas its turn off is fast (nano-seconds) as would be expected from a high speed
device like this.
The LMH6601 SD pin is a CMOS compatible input with a pico-ampere range input current drive requirement.
This pin needs to be tied to a level or otherwise the device state would be indeterminate. The device shutdown
threshold is half way between the V⁺ and V^− pin potentials at any supply voltage. For example, with V⁺ tied to
10V and V^− equal to 5V, you can expect the threshold to be at 7.5V. The state of the device (shutdown or normal
operation) is ensured over temperature as longs as the SD pin is held to within 10% of the total supply voltage.
For V⁺ = 10V, V^− = 5V, as an example:
• Shutdown Range 5V ≤ SD ≤ 5.5V
• Normal Operation Range 9.5V ≤ SD ≤ 10V
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Product Folder Links: LMH6601 LMH6601-Q1