FUNCTIONAL DEVICE OPERATION
LOGIC COMMANDS AND REGISTERS
Table 8. And/Or/SPI/Parallel Control
Table 9 defines the output frequency with the selected
input bits.
Table 9. Frequency Select
PWM Pin AND/OR
PWM
Freq/
DC EN
Bit
ON/
OFF
Bit
Rload
EN
Bit
PWM
Pin
Output
0 = en 0 = OR
1 = dis 1 = AND
Measure
Frequency Select
Bits
987
Frequency Hz
≠ 0
X
X
X
X
X
Rload
Measure
000
001
010
011
100
101
110
111
10 Hz
20 Hz
0
0
0
0
0
0
0
1
1
1
0
0
0
0
X
X
X
0
0
0
0
0
0
1
0
0
X
1
0
1
X
X
X
0
OFF
Freq/DC
ON
40 Hz
X
0
80 Hz
OFF
160 Hz
320 Hz
640 Hz
1.28 kHz
1
0
Freq/DC
ON
X
X
1
X
ON
Notes: Tolerance on selected frequency is +-10% with part
calibrated. On state short faults may not be detected if t_on_short >
1/f_pwm * duty_cycle * 0.98.Off state open faults may not be
detected if t_off_open > 1/fpwm * (1-duty_cycle) * 0.75.
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
0
X
0
X
1
0
0
1
1
X
X
0
X
0
1
OFF
OFF
Freq/DC
Freq/DC
ON
VDSNSX SHORT THRESHOLD COMMAND
The short fault threshold voltage of the external MOSFET
may be programmed via SPI. Table 10 illustrates the bit
pattern required for a particular short fault threshold. Open
load fault detect threshold is set internally to 2.5V and may
not be programmed.
PWM FREQUENCY/DUTY CYCLE COMMAND
Table 10. VDSNSx Fault Threshold Select
The PWM Frequency/Duty Cycle Command allows the
user to individually program a PWM output with a frequency
and duty cycle. Once the PWM Freq/DC registers are
programmed, the PWM output GD1, GD2, GD3 are
controlled via the AND/OR command and GD4, GD5, GD6
are controlled via the PWM pin Enable Command. Pre-driver
output control bits supersede the internal PWM controller.
GDx outputs must be commanded OFF for the controller to
function. (SeeTable 8)
PWM VDS FLT
Bits
VDSNSx Fault Threshold Select
210
543
876
000
001
010
011
100
101
110
111
0.5V
1.0V
The duty cycle of the PWM outputs is controlled by bits 0
through 6, inclusive. The duty cycle value is 1% per binary
count from 1 to 100 with counts of 101 through 127 defaulting
to 100%. For example:
1.5V
2.0
2.5V
Sending SPI WORD; 01100x1110001100
This would set PWM1 output to 1.28Khz frequency with a
12% duty cycle.
3.0V
No Change
No Change
VDSNSX SHORT FAULT TIMER COMMAND
The Short Fault Timer can be programmed via the SPI to
the values listed in Table 11, on page 24. When the 33800
detects an over-current condition, as defined by VDS
exceeding the programmed short fault voltage threshold, the
33800
Analog Integrated Circuit Device Data
Freescale Semiconductor
23
FREESCALE [ Freescale ]
