33899 datasheet(17/26 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33899

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

INTRODUCTION

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

Figure 11. Functional Block Diagram

INTRODUCTION

H-BRIDGE OUTPUT DRIVERS (S0 AND S1)

The 33899 Power IC provides the means to efficiently

drive a DC motor in both forward and reverse shaft rotation

via a monolithic H-Bridge comprising low RDS(ON) N-channel

MOSFETs and integrated control circuitry. The switching

action of the H-Bridge can be pulse-width modulated to

obtain both torque and speed control, with PWM frequencies

up to 11kHz supported with minimal switching losses.

The outputs comprise four Power MOSFETs configured as

a standard H-Bridge, controlled by the PWM input and the

FWD and REV inputs.

ANALOG CONTROL AND PROTECTION

The 33899 has integrated voltage regulators which supply

the logic and protection functions internally. This reduces the

requirements for external supplies and insures the device is

safely controlled at all times when battery voltage is applied.

An integrated charge pump provides the required bias

levels to insure the output MOSFETs turn fully ON when

commanded.

Each MOSFET provides feedback to the protection

circuitry by way of a current sensor. Each sense signal is

compared with programmable over-current levels and

produces an immediate shutdown in case of a high current

short-circuit. The low side current sense is also capable of

producing a current limiting PWM to reduce overload

conditions as determined by the programmable limits. The

high side current sense is available to the MCU as an analog

current proportional to the load current.

Each MOSFET has over-temperature protection circuitry

that disables the device. A thermal warning sets a flag in the

SPI register when the device is approaching a protection

limit.

MCU INTERFACE AND OUTPUT CONTROL

The SPI and control logic signals are compatible with both

5V and 3.3V logic systems.

The SPI provides programmable control of output slew

rate and current limits. The status register makes detailed

diagnostics available for protective and warning functions.

The output drivers are controlled by the input signals EN1,

EN2, FWD, REV, and PWM.

The low side and high side MOSFETs connected to S0 are

controlled by the PWM input when FWD is a logic [1] and

REV is a logic [0]. The low side MOSFET connected to S1 is

idle in this state. The high side MOSFET connected to S1 is

statically ON in the forward direction. The low side and high

side MOSFETs connected to S1 are controlled by the PWM

input when FWD is a logic [0] and REV is a logic [1]. The low

side MOSFET connected to S0 is idle in this state. The high

side MOSFET connected to S0 is statically ON in the reverse

direction. To reduce power during the recirculation period,

the upper recirculation MOSFET is turned on synchronously

with the OFF-time of the low side MOSFET.

MCU Interface and Output Control

MC33899 - Functional Block Diagram

Analog Control and Protection

H-Bridge

Output Drivers

S0 - S1

Direction Control

Current Sense

Voltage Regulation

Temperature Sense

Charge Pump

Analog Control and Protection

MCU Interface and Output Control

SPI Interface

H-Bridge

Command & Fault Registers

PWM Controller

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