MAX1463 データシートの表示（PDF） - Maxim Integrated

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MAX1463

Low-Power Two-Channel Sensor Signal Processor

Maxim Integrated 

Low-Power Two-Channel Sensor

Signal Processor

Typical Application Circuit

Analog ratiometric output configuration (Figure 2) pro-

vides an output that is proportional to the power-supply

voltage. Ratiometricity is an important consideration for

automotive, battery-operated instruments, and some

industrial applications.

Detailed Description

The MAX1463 is a highly integrated, low-power, two-

channel sensor signal processor optimized for industri-

al and process control applications, such as pressure

sensing and compensation, RTD and thermal couple

linearization, weight sensing and classification, and

remote process monitoring with limit indication.

The MAX1463 incorporates a 16-bit CPU, user-pro-

grammable 4kB of FLASH memory, 128 bytes of

FLASH user information, 16-bit ADC, two 16-bit DACs,

two 12-bit PWM digital outputs, four rail-to-rail op amps,

SPI interface, two GPIOs, and one on-chip temperature

sensor.

Each sensor signal can be amplified, compensated for

temperature, linearized, and the offset and full scale

can be adjusted to the desired value. The MAX1463

can provide outputs as analog voltage (DAC) or digital

(PWM, GPIOs), or simple on/off alarm indication

(GPIOs). The uncommitted op amps can be used to

provide 4–20mA outputs or for additional gain and fil-

tering. Each DAC output is routed to either a small or

large op amp. Large op amps are capable of driving

heavier external loads. The unused circuit functions

can be turned off to save power.

All sensor linearization and on-chip temperature com-

pensation is done by a user-defined algorithm stored in

FLASH memory. The user-defined algorithm is pro-

grammed over the serial interface and stored in 4kB of

integrated FLASH memory.

The MAX1463 uses an internal 4MHz oscillator or an

externally supplied 4MHz clock. CPU code execution

and ADC operation is fully synchronized to minimize

the noise interference of a CPU-based sensor proces-

sor system. The internal clock can be routed off chip for

driving external circuit components to maintain system

synchronization and to avoid clock-beat noise often

found in multiclock systems. The CPU sequentially exe-

cutes instructions stored in FLASH memory.

Sensor Input

The MAX1463 provides two differential signal inputs,

INP1-INM1 and INP2-INM2. These inputs can also be

configured as four single-ended signals. Each input

can have a common-mode range from VDD to VSS and

a programmable gain range of 0.94V/V to 240V/V. The

differential input signals are summed with the output of

the coarse offset DAC (CO DAC) for offset correction

prior to being amplified by the programmable gain

amplifier (PGA). The resulting signal is applied to the

differential input of the ADC for conversion.

The CPU can be programmed to measure one or two

differential inputs plus the internal temperature sensor

defined in user-supplied algorithm. For example, the

differential inputs can be measured many times while

the temperature can be measured less frequently.

On-Chip Temperature Sensing

The on-chip temperature sensor is a diode that changes

-2mV/°C over the operating range. The ADC converts the

temperature sensor in a similar manner as the sensor

inputs. During an ADC conversion of the temperature

sensor, the ADC automatically uses the internal 1.25V

reference as the ADC full-scale reference. The tempera-

ture data format is 15-bit plus sign in two’s-complement

format. There is no programmable gain adjustment for

the temperature sensor input. Offset compensation by

the CO DAC is provided so that the nominal temperature

measurement can be centered at the ADC output mid-

scale value. Additional digital gain and offset correction

can be provided by the CPU.

Output Format

There are two output modules in the MAX1463—DOP1

(DAC Op Amp PWM 1) and DOP2 (DAC Op Amp PWM

2). Each of the DOP modules contains a 16-bit DAC, a

12-bit digital PWM converter, a small op amp, and a

large op amp with high-output-drive capability. Each

module can be configured in several different modes to

suit a wide range of output signal requirements. Either

the DAC or the PWM can be selected as the primary

output signal. The DAC output signal must be routed to

one of the two op amps before being made available to

a device pin. See the DAC, Op Amp, PWM Modules

(DOPn) section for details. Additional digital outputs are

available on the GPIOs; 4–20mA output format can be

accomplished by using the unrouted op amp.

Initialization

A user-defined initialization routine is required to con-

figure the oscillator frequency and, if necessary, vari-

ous analog modules, e.g., PGA gain, ADC resolution,

ADC clock settings, etc. After the initialization routine,

the CPU can start execution of the main program.

Power-On Reset

The MAX1463 contains a POR circuit to disable CPU

execution until adequate VDD voltage is available for

operation. Once the power-on state has been reached,

the MAX1463 is kept under reset condition for 250µs

before the CPU starts execution. Below the VDD thresh-

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