maxq7667 Maxim Integrated Products, Inc., maxq7667 Datasheet - Page 17

• Manufacturer Part Number: maxq7667
• Description: 16-bit, Risc, Microcontroller-based, Ultrasonic Distance-measuring System
• Manufacturer: Maxim Integrated Products, Inc.

The LNA provides a 40V/V fixed gain to the input signal.
The differential inputs of the LNA are ECHOP and
ECHON. For proper biasing of the LNA, AC-couple the
transducer or any external circuitry to ECHOP and
ECHON. For a single-ended input signal, AC-couple the
signal to ECHOP with a 0.01µF capacitor and connect
ECHON to AGND through a 0.01µF capacitor placed as
close as possible to the signal source. The outputs of the
LNA connect to the inputs of a 16-bit sigma-delta ADC
and can connect internally to the AIN0 and AIN1 inputs
of the SAR ADC for external monitoring (Figure 2).
Figure 2. Echo Receive Path
ECHOP
ECHON
*R = ECHO INPUT RESISTANCE. SEE THE ELECTRICAL CHARACTERISTICS SECTION.
0V
MUX
2mV
P-P
AVDD/2
______________________________________________________________________________________
R*
R*
RCVC[7:6]:LNAISEL[1:0]
RCVC.8:LNAOSEL
Ultrasonic Distance-Measuring System
40R*
40R*
LNA
Low-Noise Amplifier (LNA)
APE.12:BGE
16-Bit, RISC, Microcontroller-Based,
MAXQ7667
TO SAR ADC
AIN0
Echo Receive Path
AIN1
RCVC[4:0]:RCVGN[4:0]
APE.13:RSARE
RECEIVE
BANDGAP REF
CLOCK
ECHO
GAIN SIGMA-
DELTA ADC
VARIABLE
AGND
2.5V
0.47µF
REFGB
TO EXTERNAL VOLTAGE
CONTROL
BPFI[15:0]
CLOCK
REFERENCE
0.47µF
REF
BANDPASS
LPFC[15:12]:FFIL[3:0]
LPFC[2.0]:FFLS[2:0]
AGND
FILTER
An analog multiplexer located at the input of the LNA
selects one of three possible signals for processing by
the echo receive path; the normal echo signal AC-cou-
pled to the ECHOP and ECHON inputs, 0V signal, or a
2mV
2mV
cycle matching the burst signal, allows the echo
receive chain to process a simulated echo.
BPFO[15:0]
LPFC.3:FFLD
TIMER 0
TIMER 1
TIMER 2
P-P
P-P
ASR.1:LPFRDY
CMPC[14:0]:CMPH[14:0]
LOWPASS FILTER
RECTIFIER PLUS
square-wave signal, with frequency and duty
FULL-WAVE
internally generated signal (Figure 2). The
CMPC.15:CMPP
CONTROL
CMPT[15:0]
AIE.1:LPFIE
FIFO
AIE.2:LFLIE
DATA READY
INTERRUPT
LPFC[11:8]:FFDP[3:0]
LPFD[15:0]
8 x 16
FIFO
LPFC.7:FFOV
ASR.2:LPFFL
AIE.3:CMPIE
ASR.12:CMPLVL
LPFF[15:0]
Diagnostic Signals
ASR.3:CMPI
17