LT5521 datasheet(14/16 Pages) LINER

14 / 16 page

LT5575

5575f

APPLICATIONS INFORMATION

Care should be taken when the demodulator’s outputs are

DC-coupled to the external load to make sure that the I/Q

mixers are biased properly. If the current drain from the

outputs exceeds 6mA, there can be signiﬁcant degrada-

tion of the linearity performance. Each output can sink no

more than 16.8mA when the outputs are connected to an

external load with a DC voltage higher than VCC – 1.1V.

The I/Q output equivalent circuit is shown in Figure 8.

In order to achieve best IIP2 performance, it is important

to minimize high frequency coupling among the baseband

outputs, RF port and LO port. For a multilayer PCB layout

design, the metal lines of the baseband outputs should be

placed on the backside of the PCB as shown in Figures 2

and 3. Typically, output shunt capacitors C1-C4 are not

required for the application near 1900MHz. However, for

other frequency bands, these capacitors can be optimized

for best IIP2 performance. For example, when the oper-

ating frequency is 900MHz, the IIP2 can be improved to

54dBm or better when 10pF shunt capacitors are placed

at each output.

Enable Interface

A simpliﬁed schematic of the EN pin is shown in Fig-

ure 9. The enable voltage necessary to turn on the LT5575

is 2V. To disable or turn off the chip, this voltage should

be below 1V. If the EN pin is not connected, the chip is

disabled. However, it is not recommended that the pin be

left ﬂoating for normal operation.

It is important that the voltage applied to the EN pin

should never exceed VCC by more than 0.3V. Otherwise,

the supply current may be sourced through the upper

ESD protection diode connected at the EN pin. Under no

circumstances should voltage be applied to the EN pin

before the supply voltage is applied to the VCC pin. If this

occurs, damage to the IC may result.

Figure 9. Enable Pin Simpliﬁed Circuit

VCC

5575 F09

60k

LT5575

LT5521 bảng dữ liệu(PDF) 14 Page - Linear Technology

LT5521 bảng dữ liệu(HTML) 14 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

bảng dữ liệu tải về

Link URL