L99MH98 datasheet(33/147 Pages) STMICROELECTRONICS

33 / 147 page

Figure 17. Extract of application diagram for temperature measurement

GH5

SH5

GL5

GH7/8

SH7/8

GL7/8

PWM1

PWM2

PWM3

CSO1

CSO2

DIODE3

DIODE4

DIODE1

DIODE2

GND

VDH

µC (input)

SH1

SH2

SH3

SH4

SH5

SH6

SH7

SH8

VProtected

GND

DIODE3

GND

DIODE4

PGND

VDH

DIAGN

logic and

diagnostics

PWMx

controller

sample and hold

Muxer

and

Current

generator

and

ADC

If a more precise temperature measurement is required, two heat map methods can be adopted:

1. The first way is to measure the temperature difference between the H-bridge MOSFET and the point where

the diode(s) is soldered through the thermal map of the application board. The temperature difference

between the two points is then saved in the memory of the microcontroller as a corrective factor: each time the

microcontroller carries out the temperature measurement through the diode it applies the previously stored

correction factor to obtain a temperature measurement of the MOSFET closest to reality.

2. The second solution is to foresee places in the PCB where the diode(s) can be soldered in order to find the

best spot to sense the temperature. By making a heat map of the application board the user will be able to

discover the most suitable place where to put the thermal sensor. In this way the measurement made by the

diode will be the closest to real MOSFET temperature. In any case, a corrective factor, as foreseen in point 1,

can be considered. The thermal sensor(s) can also be used in the normal working mode for controlling the

maximum PCB temperature.

The monitor of the external 4 diodes/chains allows to detect steady, not fast, temperature raising of specific PCB

areas; a temperature control of the module can be also implemented via the external diodes.

4.2.4

H-bridge current calculation

After having known the temperature at which the H-bridge is working and having measured the Vds, the

microcontroller will be able to evaluate the working current. To do this, the microcontroller must follow two simple

calculations:

•

Calculate Rds(on) at working temperature. The microcontroller has in its memory the trend of the variation

curve of the Rds(on) in temperature: knowing the temperature, it can estimate the value of the Rds(on) at

the temperature in which the H bridge is working.

•

Calculate the current. At this point the microcontroller has calculated the value of the Rds(on) and has

acquired the measured value of the Vds: the current flowing in the bridge H is easily calculated as the ratio

between Vds/Rds(on).

4.3

Power ON/OFF

4.3.1

Three stages gate current

A tailored gate current strategy for the Ton/off of the external MOSFETs, called “three stages gate current”, has

been implemented in the L99MH98. Behavior is showed in the Figure 18.

The new gate current strategy is implemented in the following three stages:

L99MH98

Gates driver

DS14611 - Rev 3

page 33/147

L99MH98 датащи(PDF) 33 Page - STMicroelectronics

L99MH98 датащи(HTML) 33 Page - STMicroelectronics

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 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL