33899 Datasheet, PDF (13/26 Pages) Freescale Semiconductor, Inc – Programmable H-Bridge Power IC

FUNCTIONAL DESCRIPTION
FUNCTIONAL PIN DESCRIPTION
ENABLE INPUTS (EN1, EN2)
Logic [0] in either of the Enables (EN1 or EN2) disables all
four of the output drivers (refer to Table 6). While either EN1
or EN2 is at logic [1], the 33899 is still capable of detecting
open circuit and short circuit faults on all of the outputs
interfacing with the external load(s). The EN1 and EN2 inputs
have 50μA pull-downs to ground that disable the outputs
when open circuit conditions occur.
Table 6. Enable Truth Table
EN1
EN2
Status
0
0
Disabled (Sleep Mode)
0
1
Disabled (Standby Mode)
1
0
Disabled (Standby Mode)
1
1
Enabled (Run Mode)
INPUT CONTROL OF H-BRIDGE (PWM)
commands the appropriate low side MOSFET (M2 or M4) ON
and the appropriate high side MOSFET (M1 or M3) OFF. A
logic [0] commands the appropriate low side MOSFETs (M2
or M4) OFF and the appropriate high side MOSFETs (M1 or
M3) ON. The high and low side MOSFETs that are PWM’ed
are determined by the commanded direction (FWD or REV).
If a shorted condition exists, the particular output MOSFET
will be latched off after 5.0μs to 10μs. Subsequent PWM
edges will retry to turn on the same MOSFET. Only when a
thermal fault is reached are all outputs latched off until the
clear fault bit is set by the microprocessor. Any PWM high to
low to high pulse that is shorter than 500ns keeps the low-
side MOSFET from starting to turn off. The rising edge of this
short pulse re-enables the low side MOSFET if the pulse
width is at least 200 μs long (if a short circuit latch-off had
occurred during the previous positive PWM pulse). The PWM
input has a 50μA pull-down to ground that disables all the
outputs should an open circuit condition occur.
The PWM input pin controls the sequencing of the
PWM’ing high side and low side MOSFETs. A logic [1]
High Side FET
Body Diode
S0
S1
Load Current
Both High Side
FET’s ON until
next PWM Rising
Edge
Low Side FET
Body Diode
Forward Current
Reverse Current
Current in Load
reverses polarity
PWM
FWD
REV
Figure 7. 33899 Operation in Current Reversal
Analog Integrated Circuit Device Data
Freescale Semiconductor
33899
13