Datasheet

Detailed Description
The MAX35101 is a time-to-digital converter with built-in
amplifier and comparator targeted as a complete analog
front-end solution for the ultrasonic heat meter and flow
meter markets.
With automatic differential time-of-flight (TOF) measure-
ment, this device makes for simplified computation of liq-
uid flow. Early edge detection ensures measurements are
made with consistent wave patterns to greatly improve
accuracy and eliminate erroneous measurements. Built-in
arithmetic logic unit provides TOF difference measure-
ments. A programmable receiver hit accumulator can be
utilized to minimize the host microprocessor access.
For temperature measurement, the MAX35101 supports
up to four (4) 2-wire PT1000/500 platinum resistive tem-
perature detectors (RTD).
The MAX35101 offers an event timing mode that is con-
figurable and runs cyclic algorithms to minimize micropro-
cessor interactivity and increase battery life.
The real-time clock (RTC) provides one programmable
alarm and watchdog functionality.
A simple opcode based 4-Wire SPI interface allows any
microcontroller to effectively configure the device for its
intended measurement.
On-board user flash allows the MAX35101 to be nonvola-
tile configurable and provides nonvolatile energy use data
to be logged.
Time-of-Flight (TOF) Measurement Operations
TOF is measured by launching pulses from one piezo-
electric transducer and receiving the pulses at a sec-
ond transducer. The time between when the pulses are
launched and received is defined as the time of flight. The
MAX35101 contains the functionality required to create
a string of pulses, sense the receiving pulse string, and
measure the time of flight. The MAX35101 can measure
two separate TOFs, which are defined as TOF up and
TOF down.
TIME-TO-
DIGITAL
CONVERTER
PROGRAMMABLE
ALU
DATA AND
STATUS
REGISTERS
STATE
MACHINE
CONTROLLER
PULSE
LAUNCHER
STOP_UP
TEMPERATURE MEASUREMENT
HIGH SPEED AND 32 KHZ OSCILLATORS
W/REAL TIME CLOCK
X1
4-WIRE
INTERFACE
CMP_OUT/UP_DN
ANALOG
SWITCHING AND
BIAS CONTROL
INTERNAL
LDO
MAX35101
STOP_DN
V
CC
V
CC
V
CC
BYPASS
LAUNCH_UP
LAUNCH_DN
GND GND GND GND GND
CONFIGURATION
REGISTERS
8 KBYTES
FLASH
WDO
CSW
INT
RST
SCK
DOUT
DIN
CE
X2 32KX1 32KOUT32KX0 T1 T2 T3 T4 TC
MAX35101 Time-to-Digital Converter with Analog Front-End
www.maximintegrated.com
Maxim Integrated │ 9
Block Diagram