AN4402
Application note
Multichannel drivers driving inductive loads
with L99MC6 and L9733
Introduction
The L99MC6 and the L9733 are respectively hexa and octal multi-channel drivers capable
of driving various types of loads: resistive, inductive, capacitive loads and LEDs. They
integrate an SPI interface for a high level of configurability, offering detailed device
diagnostics and protection features such as overtemperature, overcurrent detection, in
order to support robust automotive designs.
The output stages of these flexible devices consist of n-channel MOSFETs. They both have
an internal charge pump which allows all the outputs of the L9733 and three outputs of the
L99MC6 (outputs 1, 2, 3) to control loads either in high-side or in low-side configuration
without additional components. The L99MC6 outputs 4, 5 and 6 are fixed low-side drivers.
Figure 1. Block diagrams on the L99MC6 and L9733
November 2013
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Contents
AN4402
Contents
1
2
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Active clamp of the L99MC6 and L9733 . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1
2.2
Low-side configured outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
High-side configured outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.1
2.2.2
Case 1: V
BAT
≤
V
CL_LS
- V
CL_HS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Case 2: V
BAT
≥
V
CL_LS
- V
CL_HS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3
Demagnetization energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1
3.2
Low-side configured output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Calculation of the demagnetization energy . . . . . . . . . . . . . . . . . . . . . . . .11
3.2.1
3.2.2
Summary of the demagnetization energy – low-side . . . . . . . . . . . . . . . 15
Calculation example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3
High-side configured outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.3.1
3.3.2
Demagnetization energy with VBAT < VCL_LS – VCL_HS . . . . . . . . . . 17
Demagnetization energy with VBAT > VCL_LS – VCL_HS . . . . . . . . . . 19
3.4
Clamping energy at high battery voltage . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.4.1
3.4.2
3.4.3
3.4.4
Qualitative analysis when the gate-drain clamp is active . . . . . . . . . . . 21
Example of a low-side configured output of the L99MC6 . . . . . . . . . . . 23
Example of a high-side configured output of the L99MC6 . . . . . . . . . . . 24
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4
Energy capability and load compatibility . . . . . . . . . . . . . . . . . . . . . . . 27
4.1
4.2
Guideline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Example of L99MC6 driving a relay with a low-side driver . . . . . . . . . . . . 28
Appendix A Documents reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Appendix B Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Appendix C Summary of the demagnetization energy . . . . . . . . . . . . . . . . . . . . 35
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
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List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Specification of clamping voltages - L99MC6 and L9733 . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
E
DEMAG_LS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Example of application parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Energy parameters vs R
P
values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Analogies between the equations for a low-side and a high-side . . . . . . . . . . . . . . . . . . . . 17
E
DEMAG1_HS
with V
BAT
< V
CL_LS
– V
CL_HS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
E
DEMAG2_HS
with V
BAT
> V
CL_LS
– V
CL_HS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Low-side output - conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Overestimation of E
DEMAG
caused by the simplification: R
L
= 0
Ω.
. . . . . . . . . . . . . . . . . . 23
high-side output - conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Energy values vs battery voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Application conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
E
DEMAG_MAX
and corresponding t
DEMAG
for a single pulse, T
JSTART
= 150°C, R
L
= 0
Ω,
V
BAT
= 13.5 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
E
DEMAG_MAX
and corresponding t
DEMAG
for a repetitive pulse with T
JSTART
= 100 °C,
R
L
= 0
Ω,
V
BAT
= 13.5 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Demagnetization time and demagnetization energy for a low-side configured output . . . . 35
Demagnetization time and demagnetization energy for a high-side configured output . . . 36
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
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List of figures
AN4402
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Block diagrams on the L99MC6 and L9733 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Low-side and high-side configured output driving inductive loads . . . . . . . . . . . . . . . . . . . . 6
Low-side of a L99MC6 during the turn-off phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
L99MC6 high-side during the turn-off, V
BAT
< V
CL_LS
- V
CL_HS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
L99MC6 high-side during the turn-off, V
BAT
> V
CL_LS
- V
CL_HS
. . . . . . . . . . . . . . . . . . . . . . 9
Relay with spike protection resistor in parallel to the coil . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Equivalent electrical diagram during the turn-off phase of an inductive load with parallel
resistor, driven by a low-side configured output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Equivalent electrical diagram of the turn-off phase of an inductive load driven by a
low-side configured output, without parallel resistor to the load . . . . . . . . . . . . . . . . . . . . . 14
E
DEMAG_LS
vs R
P
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Equivalent circuit during the demagnetization of a high-side with parallel resistor,
V
BAT
< V
CL_LS
- V
CL_HS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Equivalent circuit during the demagnetization of a high-side with parallel resistor,
V
BAT
> V
CL_LS
- V
CL_HS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Contribution of the factor 1 / (1 - (V
CL_LS
/V
BAT
)) to the increase E
DEMAG
with V
BAT
. . . . . 22
E
DEMAG_LS
vs V
BAT
– Example of a low-side output of the L99MC6 . . . . . . . . . . . . . . . . . 23
Example - Relative E
DEMAG_LS
to E
DEMAG@VBAT=13V
versus V
BAT
/13V (No parallel
resistor) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
E
DEMAG_HS
vs V
BAT
– Example of a high-side output of the L99MC6 . . . . . . . . . . . . . . . . 25
Datasheet L99MC6 - Inductive energy capability of configurable channels, configured as
low-side switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
E
DEMAG_MAX
vs t
DEMAG
for a single pulse T
JSTART
= 150°C . . . . . . . . . . . . . . . . . . . . . . . 30
E
DEMAG_MAX
vs t
DEMAG
for repetitive pulse T
JSTART
= 100°C . . . . . . . . . . . . . . . . . . . . . . 31
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Description
1
Description
This document describes the protection features implemented in the L99MC6 and L9733 to
control inductive loads. It provides calculations of the energy dissipated in the output
MOSFETs of these devices during the switch-off phase of this type of loads in different
configurations:
•
•
The outputs are configured either as low-side or high-side drivers
With and without parallel resistor to the inductive load
Although the examples are applied to the L99MC6, general results are also applicable to
devices integrating the same type of active clamping protections.
Finally, the developers will find a guideline to verify if the outputs of these devices are
compatible with their load specifications and application conditions.
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