L99MH98 datasheet(29/147 Pages) STMICROELECTRONICS

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Gates driver

4.1

Outputs driving signals

To work with each half-bridge the following registers need:

1. HB_MODEx (half-bridge mode): this register is used to control the functionality of the single half-bridge. x

indicates the number of the half-bridge to work on, x = 1 to 8. It is a 2-bit register (see the Table 23 and

Table 24).

2. EN_PWMy (enable PWM): this 1-bit register is used to enable/disable the PWM signal, y indicates the PWM

pins that must be enabled/disabled, y = 1...3 (see the Table 24).

3. HB_PWMx (Half bridge PWM): This 3-bit register is used to indicate which PWM signal is applied to the HS or

LS of the x-th half-bridge, x = 1...8 (see the Table 24).

When a MOSFET of a half-bridge must be powered OFF or ON in the static mode the HB_MODEx register must

be used. As an example, if the HS of the half-bridge 5 and the LS of the half-bridge 6 must be powered ON the

following registers must be written:

•

HB_MODE5 = 10

•

HB_MODE6 = 01

A maximum of three PWM signals can be applied to the L99MH98. Each PWM signal can be provided to each HS

or LS of each half-bridge, using the correct programming of the registers HB_MODEx, EN_PWMy and HB_PWMx

(see the Table 24).

As an example, an H-bridge is composed of half-bridge 4 and half-bridge 6, HS of 4 is always ON while PWM 2 is

applied to the LS of half-bridge 6. In this case we have:

•

HB_MODE4 = 10 → HS of the half-bridge 4 is ON in states mode

•

EN_PWM2 = 1 → PWM2 signal is activated

•

HB_PWM6 = 001 → PWM2 signal is mapped on the LS of the half-bridge 6

•

HB_MODE6 = 11 → enable the HB6 to work in PWM mode

Configuration of the PWM map is shown in the table below:

Table 23. PWM signal application to the half-bridges

HB_PWMx

HB_MODEx

Setting

LS and HS of the half-bridge x are kept OFF (default).

LS of the half-bridge x is ON (static, no PWM), HS of the half-bridge x is OFF

HS of the half-bridge x is ON (static, no PWM), LS of the half-bridge x is OFF

000

Low-side of half-bridge x mapped on PWM1. EN_PWM1 must be set to 1

001

Low-side of half-bridge x mapped on PWM2. EN_PWM2 must be set to 1

010

Low-side of half-bridge x mapped on PWM3. EN_PWM3 must be set to 1

011

High-side of half-bridge x mapped on PWM1. EN_PWM1 must be set to 1

100

High-side of half-bridge x mapped on PWM2. EN_PWM2 must be set to 1

101

High-side of half-bridge x mapped on PWM3. EN_PWM3 must be set to 1

110

No mapping, if used the LS and HS of the half-bridge x are kept OFF

111

No mapping, if used the LS and HS of the half-bridge x are kept OFF

The PWMx input pins have an internal pull-down current in order to put the outputs in a well-known condition in

case any of the pins will no longer be driven by the microcontroller.

Four different free-wheeling strategies are available in the L99MH98: active or passive freewheeling on either

high-side or low-side MOSFETs. To choose the correct free-wheeling method the HB_WHEELx, x = 1...8, must be

programmed according to the Table 24.

L99MH98

Gates driver

DS14611 - Rev 3

page 29/147

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