PT2000 datasheet(49/148 Pages) NXP

49 / 148 page

NXP Semiconductors

PT2000

Two comparators are implemented for the VDS monitoring function of D_LS7/8. One is used for normal VDS monitoring (See LS1 - LS6

VDS monitor on page 46), and the other is a high-speed comparator used for the DC/DC resonant converter application.

Normal VDS monitoring:

• Input impedance of D_LSx has to be switched to low speed by setting lSX_VDS_HIGHSPEED_EN to “0” via the SPI register bit (refer to

Table 116, Vds7_dcdc_config (182h) & Vds8_dcdc_config (183h))

•lSX_VDS_FBK is used for diagnostics

• Clamp voltage = 3.5 V

Fast VDS monitoring (DC/DC resonant converter):

• Input impedance of D_LSx has to be switched to high speed by setting lSX_VDS_HIGHSPEED_EN to “1” via SPI register bit (refer to

Table 116, Vds7_dcdc_config (182h) & Vds8_dcdc_config (183h))

• lsx_vds_dcdc is used for resonant detection

• VDS Threshold needs to be set to 2.5 V

For more details on the DC/DC mode See DC/DC converter control (LS7/8) on page 61.

6.7

Current measurement

There are six total input pairs to measure currents with external shunt resistors in a four-wire configuration.

• Four general purpose blocks (#1, 2, 3, and 4).

• Two extended mode block for DC-DC converters (#5 and 6).

The shunt resistors are used in low-side configuration with one of the shunt terminals tied to ground for all the blocks. This means the

PT2000 measures a differential voltage over the two input pins.

6.7.1

General purpose current measurement block

The actuator current flowing in an external sense resistor is measured to implement a closed loop current control. The current

measurement block is comprised of a differential amplifier, sensing the voltage across the sense resistor, a voltage comparator, and an

8-bit current DAC.

Figure 17. General purpose current measurement block diagram

The differential amplifier gain is selectable among four different values by means of the opamapx_gain (1:0) signal, to get the suitable

signal amplification. The gain can be changed at runtime by the microcore using the stgn instruction (reference Programming Guide and

Instruction Set). The differential amplifier also adds a constant offset to its output. Therefore, the output of the amplifier is always positive.

The desired actuator current level can be selected and changed at runtime by the microcore, setting the proper dacx_Value (7:0) threshold

value in the DAC. Each current measurement channel can be used in ADC mode. A track and hold circuit is implemented to keep the

voltage at the comparator input stable during the ADC conversion.

G_LSz

Load

OA_y

dacx_value (7:0)

–

VSENSEPx

VSENSENx

–

DACx

curx_fbk

AGND

Filter x

Current Measurement (1, 2, 3, 4)

MC33PT2000

Diff Ampx

Comp x

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