MCP3551-ESLASHMS datasheet(11/30 Pages) MICROCHIP

11 / 30 page

DS21950B-page 11

MCP3551/3

3.0

PIN DESCRIPTIONS

TABLE 3-1:

PIN FUNCTION TABLES

3.1

Voltage Reference (VREF)

The MCP3551/3 devices accept single-ended refer-

ence voltages from 0.1V to VDD. Since the converter

output noise is dominated by thermal noise, which is

independent of the reference voltage, the output noise

is not significantly improved by diminishing the refer-

ence voltage at the VREF input pin. A reduced voltage

reference will significantly improve the INL perfor-

mance (see Figure 2-4); the INL max error is propor-

tional to VREF

3.2

Analog Inputs (VIN+, VIN-)

The MCP3551/3 devices accept a fully differential ana-

log input voltage to be connected on the VIN+ and VIN-

input pins. The differential voltage that is converted is

defined by VIN = VIN+ - VIN-. The differential voltage

range specified for ensured accuracy is from -VREF to

+VREF. However, the converter will still output valid and

usable codes with the inputs overranged by up to 12%

(see

Section 5.0

“Serial

Interface”)

room

temperature. This overrange is clearly specified by two

overload bits in the output code.

The absolute voltage range on these input pins extends

from VSS - 0.3V to VDD + 0.3V. Any voltage above or

below this range will create leakage currents through

the Electrostatic Discharge (ESD) diodes. This current

will increase exponentially, degrading the accuracy and

noise performance of the device. The common mode of

the analog inputs should be chosen such that both the

differential analog input range and the absolute voltage

range on each pin are within the specified operating

range defined in Section 1.0 “Electrical Characteris-

tics”.

3.3

Supply Voltage (VDD, VSS)

VDD is the power supply pin for the analog and digital

circuitry within the MCP3551/3. This pin requires an

appropriate bypass capacitor of 0.1 µF. The voltage on

this pin should be maintained in the 2.7V to 5.5V range

for specified operation. VSS is the ground pin and the

current return path for both analog and digital circuitry

of the MCP3551/3. If an analog ground plane is

available, it is recommended that this device be tied to

the analog ground plane of the Printed Circuit Board

(PCB).

3.4

Serial Clock (SCK)

SCK synchronizes data communication with the

device. The device operates in both SPI™ mode 1,1

and SPI mode 0,0. Data is shifted out of the device on

the falling edge of SCK. Data is latched in on the rising

edge of SCK. During CS high times, the SCK pin can

idle either high or low.

3.5

Data Output (SDO/RDY)

SDO/RDY is the output data pin for the device. Once a

conversion is complete, this pin will go active-low,

acting as a ready flag. Subsequent falling clock edges

will then place the 24-bit data word (two overflow bits

and 22 bits of data, see Section 5.0 “Serial Inter-

face”) on the SPI bus through the SDO pin. Data is

clocked out on the falling edge of SCK.

3.6

Chip Select (CS)

CS gates all communication to the device and can be

used to select multiple devices that share the same

SCK and SDO/RDY pins. This pin is also used to

control the internal conversions, which begin on the

falling edge of CS. Raising CS before the first internal

conversion is complete places the device in Single

Conversion mode. Leaving CS low will place the

device in Continuous Conversion mode (i.e., additional

internal conversions will automatically occur). CS may

be tied permanently low for two-wire Continuous

Conversion mode operation. SDO/RDY enters a

high-impedance state with CS high.

Pin No.

Symbol

I/O/P

Function

1VREF

Reference Voltage Analog Input Pin

2VIN+

Non-inverting Analog Input Pin

3VIN-

Inverting Analog Input Pin

4VSS

Ground Pin

SCK

Serial Clock Digital Input Pin

SDO/RDY

Data/Ready Digital Output Pin

7CS

Chip Select Digital Input Pin

8VDD

Positive Supply Voltage Pin

Type Identification: I = Input; O = Output; P = Power

MCP3551-E/MS датащи(PDF) 11 Page - Microchip Technology

MCP3551-E/MS датащи(HTML) 11 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

датащи скачать

ссылки URL