AN5108, Clock Calibration for the Dual SOIC 24 V High-side Switch Family - Application Note

Freescale Semiconductor
Application Note
Document Number: AN5108
Rev. 1.0, 4/2015
Clock Calibration
for the Dual SOIC 24 V High-side Switch Family
1
Introduction
This application note describes the clock calibration and how to use a
reference time slot of the MC06XS4200, MC10XS4200, MC20XS4200,
MC22XS4200, and MC50XS4200 devices. These intelligent high-side
switches are designed to be used in 24 V systems such as trucks,
busses, and special engines. They can be used in some industrial and
12 V applications as well. The low RDS(on) channels can control
incandescent lamps, LEDs, solenoids, or DC motors. Control, device
configuration, and diagnostics are performed through a 16-bit SPI
interface, allowing easy integration into existing applications. For a
complete feature description, refer to the individual data sheets.
© Freescale Semiconductor, Inc., 2015. All rights reserved.
Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2 Internal Clock Calibration . . . . . . . . . . . . . . . . . . . . .2
3 Timing Specification. . . . . . . . . . . . . . . . . . . . . . . . . .3
4 Reference Documents . . . . . . . . . . . . . . . . . . . . . . . .4
5 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Internal Clock Calibration
2
Internal Clock Calibration
Each channel has a fully independent PWM module activated by setting PWM_en_s. It modulates an internal or external clock signal.
Setting Clock_int_s = 1 (bit D6 of the OCR_s register) activates the internal clock, and setting Clock_int_s = 0 activates the external clock.
By using a reference time slot (usually available from an external microcontroller), the period of each of the internal PWM clocks can be
changed or calibrated.
Calibration of the default period = 1/fPWM(0) reduces its maximum variation from about 30% to 10%. The programming procedure is as
follows:
• Initialization by sending a dedicated word to the SI-CALR register.
• Next, the device sets the new value of the switching period in two steps. First it measures the time elapsed between the first falling
edge on the CSB pin and the next rising edge on the CSB pin (tCSB). Then it changes the value of the internal clock period
accordingly. The actual value of the channel's switching period is obtained by multiplying the internal clock period by 256.
Figure 1. Clock Calibration Sequence
Figure 2. Internal and External Clock Operation
AN5108 Application Note Rev. 1.0 4/2015
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Freescale Semiconductor
Timing Specification
3
Timing Specification
The timing specification related to clock calibration is detailed in Table 5. of each device datasheet. See Reference Documents.
Table 1. Calibration Timing Specification
Minimum required low time during calibration of the internal clock through CSB
tCSB(MIN)
1.0
1.5
2.0
s
Maximum allowed low time during calibration of the internal clock through CSB
tCSB(MAX)
70
100
130
s
Figure 3 provides a description of specified timings converted to frequencies, as well as frequency ranges where the frequency target is
preferred.
Figure 3. Calibration Timing Specification
When the duration of the negative CSB pulse is outside a predefined time slot (from tCSB(MIN) to tCSB(MAX)), the calibration event is ignored
and the internal clock frequency remains unchanged. If the value (fPWM(0)) has not been previously calibrated, it remains at its default level.
AN5108 Application Note Rev. 1.0 4/2015
Freescale Semiconductor
3
Reference Documents
4
Reference Documents
Table 2. AN5108 Reference Documents
Description
URL
MC06XS4200 Data Sheet
http://www.freescale.com/files/analog/doc/data_sheet/MC06XS4200.pdf
MC10XS4200 Data Sheet
http://www.freescale.com/files/analog/doc/data_sheet/MC10XS4200.pdf
MC20XS4200 Data Sheet
http://www.freescale.com/files/analog/doc/data_sheet/MC20XS4200.pdf
MC22XS4200 Data Sheet
http://www.freescale.com/files/analog/doc/data_sheet/MC22XS4200.pdf
MC50XS4200 Data Sheet
http://www.freescale.com/files/analog/doc/data_sheet/MC50XS4200.pdf
AN5108 Application Note Rev. 1.0 4/2015
4
Freescale Semiconductor
Revision History
5
Revision History
Revision
Date
1.0
4/2015
Description of Changes
Initial release
AN5108 Application Note Rev. 1.0 4/2015
Freescale Semiconductor
5
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© 2015 Freescale Semiconductor, Inc.
Document Number: AN5108
Rev. 1.0
4/2015