TL851
SONAR RANGING CONTROL
SLSS004 – SEPTEMBER 1983 – REVISED MARCH 1988
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
D
Designed for Use With the TL852 in Sonar
Ranging Modules Like the SN28827
D
Operates With Single Supply
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Accurate Clock Output for External Use
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Synchronous 4-Bit Gain Control Output
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Internal 1.2-V Level Detector for Receive
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TTL-Compatible
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Interfaces to Electrostatic or Piezoelectric
Transducers
description
The TL851 is an economical digital I
2
L 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 (V
CC
) 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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V
CC
XMIT
GND
GCD
GCA
GCB
GCC
REC
BLNK
BINH
INIT
FILT
XTAL2
XTAL1
OSC
ECHO
N PACKAGE
(TOP VIEW)
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