THS4552 Datasheet, PDF (44/71 Pages) Texas Instruments – Dual-Channel, Low-Noise, Precision, 150-MHz, Fully Differential Amplifier

THS4552
SBOS831 – DECEMBER 2016
www.ti.com
10.1.5 Operating the Power Shutdown Feature
The CMOS input pin must be asserted to the desired voltage for operation. An internal pullup resistor is not
provided on the PD pin so that off-state quiescent current can be minimized. For applications simply requiring the
device to be powered on when the supplies are present, tie the PD pin to the positive supply voltage.
The disable operation is referenced from the negative supply, normally ground. For split-supply operation, with
the negative supply below ground, a disable control voltage below ground is required to turn the THS4552 off. To
assure an off state condition, the disable control pin must be below a voltage within 0.55 V of the negative
supply.
For single-supply operation, a minimum of 1.15 V above the negative supply (ground in this case) is required to
assure on operation. This logic threshold range allows direct operation from a 1.8-V supply logic when the
THS4552 operates with a single positive supply and ground.
10.1.6 Channel-to-Channel Crosstalk
Multichannel amplifiers are often used to save space and cost. Proper printed circuit board (PCB) layout
techniques can improve the crosstalk performance of multichannel amplifiers. The major cause of crosstalk is the
capacitive coupling of the signal from one channel to the other. Following are some considerations to be taken
into account to minimize the channel-to-channel crosstalk for a dual-channel THS4552:
• Use 0.1-μF or 0.01-μF SMT ceramic bypass capacitors as close as possible to the power-supply pins on each
channel
• Use a very large ground plane on the PCB and power-supply plane for each supply voltage, if possible
• Keep input pin traces to a minimum length; longer traces result in more stray capacitance
• If the design allows, put guard traces around the input pins of the amplifier; connect these guard traces to the
ground plane for high isolation
• Keep the ground return path of the load routed away from the amplifier input traces
• Isolate the traces for each amplifier from the other amplifiers as much as possible
Figure 80 shows the channel-to-channel crosstalk measurement for the THS4552 with a 2-V_PP, single-ended
sinusoidal input applied on one channel and crosstalk measured on other channel with G = 1 V/V on both
channels.
-85
+3 V
-90
+5 V
-95
-100
-105
-110
-115
-120
-125
100k
1M
Frequency (Hz)
10M
D083
Figure 80. THS4552PW Crosstalk vs Frequency
44
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