TI TL851

TL851
SONAR RANGING CONTROL
SLSS004 – SEPTEMBER 1983 – REVISED MARCH 1988
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Designed for Use With the TL852 in Sonar
Ranging Modules Like the SN28827
Operates With Single Supply
Accurate Clock Output for External Use
Synchronous 4-Bit Gain Control Output
Internal 1.2-V Level Detector for Receive
TTL-Compatible
Interfaces to Electrostatic or Piezoelectric
Transducers
VCC
XMIT
GND
GCD
GCA
GCB
GCC
REC
1
16
2
15
3
14
4
13
5
12
6
11
7
10
8
9
BLNK
BINH
INIT
FILT
XTAL2
XTAL1
OSC
ECHO
description
The TL851 is an economical digital I2L ranging control integrated circuit designed for use with the Texas
Instruments TL852 sonar ranging receiver integrated circuit.
The TL851 is designed for distance measurement from six inches to 35 feet. The device has an internal oscillator
that uses a low-cost external ceramic resonator. With a simple interface and a 420-kHz ceramic resonator, the
device will drive a 50-kHz electrostatic transducer.
The device cycle begins when Initiate (INIT) is taken to the high logic level. There must be at least 5 ms from
initial power-up (VCC) to the first initiate signal in order for all the device internal latches to reset and for the
ceramic-resonator-controlled oscillator to stabilize. The device will transmit a burst of 16 pulses each time INIT
is taken high.
The oscillator output (OSC) is enabled by INIT. The oscillator frequency is the ceramic resonator frequency
divided by 8.5 for the first 16 cycles (during transmit) and then the oscillator frequency changes to the ceramic
resonator frequency divided by 4.5 for the remainder of the device cycle.
When used with an external 420-kHz ceramic resonator, the device internal blanking disables the receive input
(REC) for 3.8 ms after initiate to exclude false receive inputs that may be caused by transducer ringing. The
internal blanking feature also eliminates echos from objects closer than 1.3 feet from the transducer. If it is
necessary to detect objects closer than 1.3 feet, then the internal blanking may be shortened by taking the
blanking inhibit (BINH) high, enabling the receive input. The blanking input (BLNK) may be used to disable the
receive input and reset ECHO to a low logic level at any time during the device cycle for selective echo exclusion
or for a multiple-echo mode of operation.
The device provides a synchronous 4-bit gain control output (12 steps) designed to control the gain of the TL852
sonar ranging receiver integrated circuit. The digital gain control waveforms are shown in Figure 2 with the
nominal transition times from INIT listed in the Gain Control Output Table.
The threshold of the internal receive level detector is 1.2 V. The TL851 operates over a supply voltage range
of 4.5 V to 6.8 V and is characterized for operation from 0°C to 40°C.
Copyright  1988, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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1
TL851
SONAR RANGING CONTROL
SLSS004 – SEPTEMBER 1983 – REVISED MARCH 1988
GAIN CONTROL OUTPUT TABLE
STEP
NUMBER
GCD
GCC
GCB
GCA
TIME (ms)
FROM INITIATE↑†
0
1
2
3
4
5
6
7
8
9
10
11
L
L
L
L
L
L
L
L
H
H
H
H
L
L
L
L
H
H
H
H
L
L
L
L
L
L
L
H
L
L
H
H
L
L
H
H
L
H
L
H
L
H
L
H
L
H
L
H
2.38 ms
5.12 ms
7.87 ms
10.61 ms
13.35 ms
16.09 ms
18.84 ms
21.58 ms
27.07 ms
32.55 ms
38.04 ms
INIT ↓
† This is the time to the end of the indicated step and assumes a nominal
420-kHz ceramic resonator.
functional block diagram
VCC
FILT
13
1
Filtered Supply
420-kHz
Oscillator
XTAL1
XTAL2
11
Frequency
Divider
10
Gain Step
Counter
G
2
5
12
6
+ 8.5
7
+
+ 4.5
XMIT
Transmit Enable
CT≤16
4
CLR
INIT
OSC
GCA
GCB
GCC
GCD
CT ≥ 208
14
CLR CT > 16
Internal
Blanking
Blanking
Latch
BINH
BLNK
REC
15
S
16
R
Echo
Latch
R
8
1.2 V
GND
2
3
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9
ECHO
TL851
SONAR RANGING CONTROL
SLSS004 – SEPTEMBER 1983 – REVISED MARCH 1988
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†
Voltage range at any pin with respect to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 0.5 V to 7 V
Voltage range at any pin with respect to VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 7 V to 0.5 V
Continuous total dissipation at (or below) 25°C free-air temperature (see Note 1) . . . . . . . . . . . . . . . 1150 mW
Operating free-air temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 40°C
Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 150°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C
† Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. This is a stress rating only, and
functional operation of the device at these or any other conditions beyond those indicated in the recommended operating conditions section of this
specification is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: For operation above 25°C, derate linearly at the rate of 9.2 mW/°C.
recommended operating conditions
Supply voltage, VCC
High-level input voltage, VIH
BLNK, BINH, INIT
Low-level input voltage, VIL
BLNK, BINH, INIT
MIN
MAX
4.5
6.8
2.1
5
Operating free-air temperature, TA
0
V
V
0.6
Delay time, power up to INIT high
UNIT
V
ms
40
°C
electrical characteristics over recommended ranges of supply voltage and operating free-air
temperature
PARAMETER
TEST CONDITIONS
Input current
BLNK, BINH, INIT
High-level output current, IOH
ECHO, OSC, GCA, GCB, GCC, GCD
Low-level output current, IOH
ECHO, OSC, GCA, GCB, GCC, GCD
On-state output current
SMIT output
Internal blanking interval
REC input
Frequency during 16-pulse
16 pulse transmit period
Frequency after 16-pulse
16 pulse transmit period
Supply current,
current ICC
MIN
TYP‡
VI = 2.1 V
VOH = 5.5 V
IOL = 1.6 mA
VO = 1 V
OSC output
93.3§
XMIT output
0
During transmit period
1
mA
µA
0.4
XMIT output
V
mA
ms
kHz
kHz
260
After transmit period
UNIT
100
–140
2.38§
49.4§
49.4§
OSC output
MAX
55
mA
‡ Typical values are at VCC = 5 V and TA = 25°C.
§ These typical values apply for a 420-kHz ceramic resonator.
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• DALLAS, TEXAS 75265
3
TL851
SONAR RANGING CONTROL
SLSS004 – SEPTEMBER 1983 – REVISED MARCH 1988
schematics of inputs and outputs
EQUIVALENT OF BLNK, BINH AND
INIT INPUTS
TYPICAL OF ECHO, OSC, GCA, GCB,
GCC, AND GCD OUTPUTS
XMIT OUTPUTS
VCC
Ref
Input
Output
5Ω
Output
500 Ω
Step No.
0
1
2
3
4
5
6
7
8
9
10
INIT
GCA
GCB
GCC
GCD
Figure 1. Digital Gain Control Waveforms
4
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• DALLAS, TEXAS 75265
11
TL851
SONAR RANGING CONTROL
SLSS004 – SEPTEMBER 1983 – REVISED MARCH 1988
VCC
INIT
16 Pulses
XMIT
BINH
BLNK
(L)
(L)
Internal
Blanking
≈ 2.38 ms
REC
≈ 1.2 V
(Input from TL852)
ECHO
Figure 2. Example of Single-Echo-Mode Cycle When Used With the
TL852 Receiver and 420-kHz Ceramic Resonator
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