Vga clamp, Power-down, Overload recovery – Rainbow Electronics MAX2036 User Manual

Page 15: Octal continuous wave (cw) mixer

MAX2036

Ultrasound VGA Integrated

with CW Octal Mixer

______________________________________________________________________________________

VGA Clamp

A clamp is provided to limit the VGA output signals to
avoid overdriving the ADC or to prevent ADC saturation.
Set VG_CLAMP_MODE low to clamp the VGA differential
outputs at 2.2V

P-P

. Set the VG_CLAMP_MODE high to

disable the clamp.

Power-Down

The device can also be powered down with PD. Set PD
to logic-high for power-down mode. In power-down
mode, the device draws a total supply current of 27mA.
Set PD to a logic-low for normal operation

Overload Recovery

The device is also optimized for quick overload recov-
ery for operation under the large input-signal conditions
that are typically found in ultrasound input buffer
imaging applications. See the

Typical Operating

Characteristics

for an illustration of the rapid recovery

time from a transmit-related overload.

Octal Continuous Wave (CW) Mixer

The MAX2036 CW mixers are designed using an active
double-balanced topology. The mixers achieve high
dynamic range and high-linearity performance, with
exceptionally low noise, which is ideal for ultrasound
CWD signal reception. The octal quadrature mixer
array provides noise performance of -155dBc/Hz at
1kHz from a 1.25MHz carrier, and a two-tone, third-
order, ultrasound-specific intermodulation product of
typically -50dBc. See the

Ultrasound-Specific IMD3

Specification

in the

Applications Information section.

The octal array exhibits quadrature and in-phase differ-
ential current outputs (CW_QOUT+, CW_QOUT-,
CW_IOUT+, CW_IOUT-) to produce the total CWD
beamformed signal. The maximum differential current
output is typically 3mA

P-P

and the mixer output-compli-

ance voltage ranges from 4.75V to 12V.

CHANNEL 1

I/Q

DIVIDER

PHASE

SELECTOR

5-BIT

I Q

DIN

CLK

LO_LVDS+

LO_LVDS-

CWIN1

CWIN2

CWIN8

GND

CW_M2

CW_M1

CW_IOUT+

DOUT

LOW_PWR

CW_IOUT-

CW_QOUT-

CW_QOUT+

CW_IOUT2+

CW_QOUT2-

LOAD

LO1

LO2

LO8

REF

CW_FILTER

M4_EN

•

• • •
• • •

• • •

•

MAX2036

I Q

CHANNEL 2

I/Q

DIVIDER

PHASE

SELECTOR

CHANNEL 8

I/Q

DIVIDER

PHASE

SELECTOR

High-Level CW Mixer and Programmable

Beamformer Functional Diagram