LTC6946 datasheet(33/54 Pages) LINER

33 / 54 page

LTC2000A

2000afb

For more information www.linear.com/LTC2000A

OPERATION

Measuring Internal Junction Temperature (TJ)

TheLTC2000Atestmultiplexermayalsobeusedtoconnect

internal junction temperature measurement diodes to the

TSTP/N pins. Ensure LMX_EN = 0 (register address 0x18)

and use SPI register 0x19 to set TDIO_EN = 1 to enable

this function (Table 9). There are two methods the user can

choose from to measure internal junction temperature (TJ).

For TDIO_SEL = 0, an unbiased NPN transistor is diode-

connectedbetweentheTSTP/Npinswithaseriesresistance

of approximately 350Ω. This diode is suitable for use with

external temperature sensors which offer series resistance

cancellation such as the LTC2991 or LTC2997.

If such a temperature sensor is not available, set

TDIO_SEL=1todirectlyobserveatemperaturedependent

voltage between TSTP and TSTN. The typical expected

voltageatTSTPisVTSTP=2.02V–5.5mV/°C•(TJ–25°C).

The junction temperature can be calculated as TJ=25°C+

(2.02V – VTSTP)/(5.5mV/°C). For best accuracy with

TDIO_SEL = 1, use TSTN to sense GND at the bottom of

the diode and calibrate the voltage at a known tempera-

ture. Typical uncalibrated accuracy is ±5°C.

Pattern Generator

A 64 sample deep pattern generator is included in the

LTC2000A to simplify system development and debug. The

patterngeneratorallowstheusertosendarepeating64sample

pattern to the DAC, completely independent of the presence

or absence of valid signals on DCKIP/N, DAP/N, and DBP/N.

Table 9. Internal Junction Temperature SPI Registers

ADDRESS

BIT

NAME

DESCRIPTION

0x19

TDIO_EN TSTP/N Junction Temperature Diode Enable. Set TDIO_EN = 1 to measure internal junction temperature (TJ) at TSTP/N.

Ensure LMX_EN = 0 when TDIO_EN = 1.

TDIO_SEL Selects which internal temperature diode is observable at TSTP/N.

For TDIO_SEL = 1, the typical voltage at TSTP with respect to TSTN is VTSTP = 2.02V – 5.5mV/°C • (TJ – 25ºC).

Junction temperature can be calculated as TJ = 25°C + (2.02V – VTSTP)/(5.5mV/°C). Typical accuracy is ±5°C.

For TDIO_SEL = 0, an unbiased diode is connected b/w TSTP/N for use with external temperature sensors.

Note: Register 0x19 resets to 0x00 (default).

To use this feature, do the following:

1. Set DCKO_DIV = 0 in register 0x02, DATA_SP = 0 and

DATA_EN = 0 in register 0x04, and PGEN_EN = 0 in

2. Write128bytesofpatterndatatoaddress0x1F(PGEN_D)

to fill the pattern generator with 64 samples. Data is writ-

ten MSB first, and will be applied to the DAC in the order

written. Data may be written one byte at a time or in larger

multi-bytewords.FortheLTC2000A-14andLTC2000A-11,

datashouldbeleftjustifiedwithzerosfillingtheremaining

two (LTC2000A-14) or five (LTC2000A-11) bits.

3. Set PGEN_EN = 1 to start the pattern generator.

4. Wait at least 1ms to ensure that the synchronizer has

initialized.

5. Set DATA_EN = 1 in register 0x04. The DAC will then

begin to output the 64 sample pattern.

The pattern generator will send the repeating 64 sample

pattern to the DAC until the user writes PGEN_EN = 0 or

DATA_EN = 0.

To read back the pattern, set DATA_EN = 0 and PGEN_EN

= 0 and then read 128 bytes from address 0x1F. Note that

thestartingpointofthepatternmayhavechangedwhilethe

pattern was running. To modify the pattern, set DATA_EN =

0 and PGEN_EN = 0 and write a new 64 sample pattern to

address 0x1F. Ensure PGEN_EN = 0 when reading or writ-

ing to address 0x1F, and always read or write an entire 64

sample pattern prior to setting PGEN_EN = 1. See Table 10.

Table 10 – Pattern Generator SPI Registers

ADDRESS BIT

NAME

DESCRIPTION

0x1E

PGEN_EN Pattern Generator Enable. Set PGEN_EN = 1 to use the internal 64 sample pattern generator to provide data to the DAC.

Set DATA_SP = 0, DCKO_DIV = 0, and DATA_EN = 1 when PGEN_EN = 1.

0x1F

[7:0] PGEN_D

Pattern Generator Data. Write 128 bytes of data to this address to fill the pattern generator with 64 samples.

Data is written MSB first. Reading this location causes the pattern generator data to be shifted out through SDO.

Ensure PGEN_EN = 0 when reading or writing to address 0x1F. Read or write an even number of bytes to address

0x1F prior to setting PGEN_EN = 1 to avoid corrupting the data inside the pattern generator.

Note: Registers 0x1E and 0x1F reset to 0x00 (default).

LTC6946 датащи(PDF) 33 Page - Linear Technology

LTC6946 датащи(HTML) 33 Page - Linear 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 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

датащи скачать

ссылки URL