L99MD01 datasheet(8/54 Pages) STMICROELECTRONICS

8 / 54 page

Detailed description

L99MD01

8/54

Doc ID 17242 Rev 6

2.5

SMPS Switched Mode Power Supply

External MOSFET

Spread spectrum technique:

●

Wobble oscillator, programmable by SPI (1.95 K / 3.9 K / 7.8 K / 15.6 KHz).

●

Frequency modulation programmable by SPI (0 / 5 / 10 / 20%).

VS2 level concept:

●

Microcontroller measuring pulse of SMPS frequency (dependent on internal oscillator

frequency).

Due to the Oscillator frequency of L99MD01 the µC can calculate the on/off counts to

program the SMPS frequency and duty cycle.

●

Microcontroller sending by SPI SMPS 6-bit on counter value, microcontroller sending

by SPI SMPS 6-bit off counter value.

Basing on the on and off counter value the duty cycle and the SMPS frequency can be

programmed.

The VS2 voltage is strongly related to the duty cycle of SMPS.

2.6

Current monitor

The current monitor output sources a current image at the current monitor output which has

a programmable ratio (1/250, 1/500, 1/750, 1/1000) of the instantaneous current of the

selected half bridge (high-side or low-side). Via SPI it can be programmed which of the

outputs are multiplexed to the current monitor output.

The current monitor output allows a more precise analysis of the actual state of the load

rather than the detection of an open or overload condition. For example this can be used to

detect the motor state (starting, free-running, stalled).

2.7

Inductive loads

Each half bridge is built by an internally connected high-side and a low-side power DMOS

transistor. Due to the built-in reverse diodes of the output transistors, inductive loads can be

driven at the outputs.

2.8

Diagnostic functions

All diagnostic functions (over/open-load, temperature warning and thermal shutdown,

over/undervoltage) are internally filtered and the condition has to be valid for at least 32 µs

(open-load: typ. 2 ms, respectively) before the corresponding status bit in the status

registers is set. The filters are used to improve the noise immunity of the device. Open-load

and temperature warning function are intended for information purpose and not changes the

state of the output drivers. On contrary, the overload and thermal shutdown condition

disables the corresponding driver (overload) or all drivers (thermal shutdown), respectively.

The microcontroller has to clear the overcurrent status bit to reactivate the corresponding

driver.

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