33899 Datasheet, PDF (17/26 Pages) Freescale Semiconductor, Inc – Programmable H-Bridge Power IC

FUNCTIONAL INTERNAL BLOCK DESCRIPTION
INTRODUCTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
MC33899 - Functional Block Diagram
Analog Control and Protection
H-Bridge
Current Sense
Voltage Regulation
Temperature Sense
Charge Pump
MCU Interface and Output Control
SPI Interface
Direction Control
Output Drivers
S0 - S1
Command & Fault Registers
PWM Controller
Analog Control and Protection
MCU Interface and Output Control
H-Bridge
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 R_DS(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.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33899
17