
MAXQ7667
16-Bit, RISC, Microcontroller-Based,
Ultrasonic Distance-Measuring System
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9
BURST OUTPUT FREQUENCY
vs. TEMPERATURE
MAXQ7667
toc01
TEMPERATURE (
°C)
BURST
OUTPUT
FREQUENCY
(kHz)
50
25
100
75
0
-25
49.96
49.97
49.98
49.99
50.00
50.01
50.02
50.03
50.04
50.05
49.95
-50
125
USING PLL
LOWPASS FILTER OUTPUT
vs. ECHO INPUT AMPLITUDE
MAXQ7667
toc02
ECHO INPUT AMPLITUDE (VP-P)
LPF
OUTPUT
(LSB)
0.04
0.02
0.08
0.06
24,576
32,768
8192
16,384
40,960
49,152
57,344
65,536
0
0.10
PROGRAMMABLE ECHO GAIN = MINIMUM
LOWPASS FILTER OUTPUT
vs. ECHO INPUT FREQUENCY
MAXQ7667
toc03
ECHO INPUT FREQUENCY (kHz)
LPF
OUTPUT
(LSB)
55
40
85
70
1000
100
10,000
100,000
10
25
100
PROGRAMMABLE ECHO GAIN = MINIMUM
ECHO INPUT AMPLITUDE = 20mVP-P
BANDPASS FILTER OUTPUT NOISE FLOOR
vs. BANDPASS FILTER CENTER FREQUENCY
MAXQ7667
toc04
FREQUENCY (kHz)
BANDPASS
FILTER
OUTPUT
(LSB
RMS
)
80
60
40
9
3
6
12
15
0
20
100
RECEIVE PATH GAIN AT MAXIMUM
TA = +105
°C
TA = +25
°C
TA = -40
°C
RECEIVE PATH RESPONSE TIME
(ECHO INPUT TO LOWPASS FILTER OUTPUT)
MAXQ7667
toc05
TIME (
s)
ADC
COUNT
(LSB)
400
200
800
600
6000
4000
10,000
2000
8000
14,000
12,000
16,000
0
1000
MINIMUM ECHO GAIN
20mVP-P ECHO AMPLITUDE
50kHz ECHO FREQUENCY
250ksps
INPUT ON
INPUT OFF
LOWPASS FILTER OUTPUT RIPPLE vs. TIME
MAXQ7667
toc06
TIME (ms)
LPF
OUTPUT
(LSB)
24
6
10
8
12,500
12,000
14,500
11,500
14,000
10,500
13,000
11,000
13,500
15,000
10,000
012
MINIMUM ECHO GAIN
20mVP-P ECHO AMPLITUDE
50kHz ECHO FREQUENCY
250ksps
SAR ADC OFFSET ERROR
vs. TEMPERATURE
MAXQ7667
toc07
TEMPERATURE (
°C)
OFFSET
ERROR
(mV)
075
25
-25
100
50
0.5
-0.5
0
1.0
1.5
2.0
-1.0
-50
125
VAVDD = 3.3V
VAVDD = 3.6V
VAVDD = 3V
Typical Operating Characteristics
(VDVDDIO = +5V, VAVDD = +3.3V, VDVDD = +2.5V, fSYSCLK = 16MHz, burst frequency = bandpass frequency = 50kHz, TA = +25°C,
unless otherwise noted.)