CS3301

DS595F2

11

2.1.3

Differential Signals

Analog signals into and out of the CS3301 are dif-

ferential, consisting of two halves with equal but

opposite magnitude varying about a common mode

voltage.

A full scale 5 Vpp differential signal centered on a

-0.15 V common mode can have:

SIG+ = -0.15 V + 1.25 V = 1.1 V

SIG- = -0.15 V - 1.25 V = -1.4 V

SIG+ is +2.5 V relative to SIG-

For the reverse case:

SIG+ = -0.15 V - 1.25 V = -1.4 V

SIG- = -0.15 V + 1.25 V = 1.1 V

SIG+ is -2.5 V relative to SIG-

The total swing for SIG+ relative to SIG- is

can be done for SIG- relative to SIG+. Note that a

common mode voltage never exceeds 1.1 V and

never drops below -1.4 V on either half of the sig-

nal.

By definition, differential voltages are to be mea-

sured with respect to the opposite half, not relative

to ground. A multimeter differentially measuring

between SIG+ and SIG- in the above example

2.2

Digital Signals

2.2.1

Clock Input

The clock signal is used by the chopper-

stabilization circuitry of the amplifier analog in-

puts. The CLK pin can be driven by an external

clock source for synchronous operation, or CLK

can be grounded to run from its own internally gen-

erated clock signal. The CLK pin is connected to a

clock detect circuit which will disable the internal

clock and use an external clock if one is supplied.

If the internal clock signal is to be used, the CLK

pin should be connected to DGND.

2.2.2

Gain Selection

The CS3301 supports gain ranges of x1, x2, x4, x8,

x16, x32, and x64. They are selected using the

GAIN0, GAIN1, and GAIN2 pins as shown in

Table 1 on page 8.

2.2.3

Mux Selection

The analog inputs to the amplifier are multiplexed,

with external signals applied to the INA+, INA- or

INB+, INB- pins. An internal termination is also

available for noise tests. Input mux selection is

made using the MUX0 and MUX1 pins as shown in

Table 1 on page 8.

Although a mux selection is provided to enable the

INA and INB switches simultaneously, significant

current should not be driven through them in this

mode. The CS3301 mux switches will maintain

good linearity only with minimal signal currents.

2.2.4

Low Power Selection

For applications where power is critical, a low-

power mode can be selected. This mode reduces

amplifier power consumption at the expense of

slightly degraded performance. Low power mode

is selected using the LPWR pin, which is active

high.

2.2.5

Power Down Selection

A power-down mode is available to shut down the

amplifier when not in use. When enabled, all inter-

nal circuitry is disabled, the analog inputs and out-

puts go high-impedance, and the device enters a

micro-power state. Power down mode is selected

using the PWDN pin, which is active high.

2.3

Power Supplies

2.3.1

Analog Power Supplies

The analog power pins of the CS3301 are to be sup-

plied with a total of 5 V between VA+ and VA-.

This voltage is typically from a bipolar

power supply. When using bipolar power supplies,

the analog signal common mode voltage should be

biased to 0 V. The analog power supplies are rec-