General Description
The HT45R37 is a TinyPower
TM
C/R to F Type 8-bit high
performance RISC architecture mICrocontroller. As a C/R
to F type of MCU, the device can interface to 16 external
C or R type sensors and convert their values to a fre -
quency value for processing. In addition its internal A/D
converter allows the device to interface directly to analog
signals and its integrated dual channel Pulse Width Modu -
lators allows control of external motors, LEDs etc.
With their fully integrated SPI and I
2
C functions, design-
ers are provided with a means of easy communication
with external peripheral hardware. The benefits of inte -
grated A/D, C/R to F converter, and PWM functions, in
addition to low power consumption, high performance,
I/O flexibility and low-cost, provides the device with the
versatility for a wide range of products in the home appli -
ance and industrial application areas. Some of these
products could include electronic metering, environmen -
tal monitoring, handheld instruments, electronically con -
trolled tools, motor driving in addition to many others.
The unique Holtek TinyPower technology also gives the
devices extremely low current consumption characteris -
tics, an extremely important consideration in the present
trend for low power battery powered applications. The
usual Holtek MCU features such as power down and
wake-up functions, oscillator options, programmable
frequency divider, etc. combine to ensure user applica -
tions require a minimum of external components.
Features

Operating voltage:
f
SYS=32768Hz: 2.2V~5.5V
f
SYS=4MHz: 2.2V~5.5V
f
SYS=8MHz: 3.0V~5.5V
f
SYS=12MHz: 4.5V~5.5V
 OTP Program Memory: 4K 15
 RAM Data Memory: 160 8
 27 bidirectional I/O lines
 Three external interrupt input shared with I/O lines

Two 8-bit programmable Timer/Event Counter
with overflow interrupt and 7-stage prescaler

External C/R to F converter
 16-Channel Capacitor/Resistor sensor inputs

Integrated Crystal, IRC, ERC and RTC oscillator
 Fully integrated internal RC oscillator available with
three frequencies: 4MHz, 8MHz or 12MHz
 Watchdog Timer function

LIRC or RTC oscillator function for watchdog timer
 PFD and Buzzer for audio frequency generation

Dual Serial Interfaces: SPI and I
2
C
 4 operating modes: normal, slow, idle and sleep
 6-level subroutine nesting

6-channel 12-bit resolution A/D converter
 2-channel 12-bit PWM output shared with I/O line
 Low voltage reset function - 2.1V, 3.15V, 4.2V
 Low voltage detect function - 2.2V, 3.3V, 4.4V
 Bit manipulation instruction
 15-Bit table read instructions
 63 powerful instructions
 Up to 0.33s instruction cycle with 12MHz system
clock at V
DD=5V
 All instructions executed in one or two machine
cycles
 Idle/Sleep mode and wake-up functions to reduce
power consumption

Time-Base and RTC interrupt
 20-pin DIP/SOP, 24/28-pin SKDIP/SOP/SSOP and
32-pin QFN packages