FUNCTIONAL DEVICE OPERATION
LOGIC COMMANDS AND REGISTERS
greater than 0.0mA. Commands outside of this command
range will automatically lock out dither.
current. The switching frequency and accuracy are
dependent upon the load inductance and resistance, battery
voltage, dither amplitude and frequency, switch points, and
the commanded current.
Programming the solenoid current begins by sending the
CCD2 Control command. The command consists of an
control address, Diagnostic Pull-up Enable bit (Diag_pu_EN),
Dither Disable bit (DTHR_DIS), and a 9-bits of data for digital
to analog conversion (DAC). The data is received and the
DAC provides bias for a comparator to produce a threshold
level. The comparator drives a switch control circuit which
generates a frequency modulated signal for the output drive.
The differential voltage across the sense resistor provides
the feedback necessary to maintain the desired output
current. The output current is continuously monitored as a
differential voltage across the internal sense resistor. When
the current is recirculation and the driver is in the off state, the
current will decay to the lower limit switch point. When the
current reaches the lower limit, the driver will turn on to
increase the current until the upper limit switch point is
reached. The output current will continue to switch between
the switch points, resulting in the desired average current.
The switch points are set to a fixed +/-5% of the commanded
Current dither is a method by which the average current is
increased and decreased through the solenoid valve. The
33800 allows the user to program the frequency and
amplitude of the dither control. Dither amplitude is
implemented by increasing and decreasing the DAC by the
programmed dither value. The rate at which the value is
changed is set by the programmed dither frequency. When
reprogramming the dither amplitude or dither frequency, the
update will occur on the start of a positive cycle.
The maximum value of the output (DAC + Dither) must be
less than 232mA. When a greater value is programmed, the
device will disable dither on the output. Similarly, the
minimum value of the output (DAC - Dither) must be greater
than 0.0mA. Requesting a lower value will disable dither on
the output.
Table 18. CCD2 Constant Current Controller Commands
Command
Control Address
14 13 12
CCD2 Command Address
Command Bits
15
11
10
9
8
0
7
0
6
5
4
3
2
1
0
0
0
Diag DTHR
Pull- DIS
up
9 BIT DAC Command Data
CCD2 Control
1
1
0
0
0
0
0
0
0
0
0
0
0 = Pull-down Current Source
1 = Pull-up Current Source
CCD2 Command Address
CCD2
Retry
Dither Amplitude
Dither Frequency
CCD2 Frequency & Amplitude
1
1
0
0
1
1
X
X
X
0
1
1
0
1
0
0
VCAL
Next SO Response (Message 2)
0 = No Fault, 1 = Fault
OvrVlt Reset Trim
,TLim
or
CAL
Flt
Open Short Open Short Fault Fault Fault Fault Fault Fault Fault Fault
Set (23)Status Fault Fault Fault Fault StatusStatusStatusStatusStatusStatusStatusStatus
int=0
CCD2 CCD2 CCD1 CCD1 OUT8 OUT7 OUT6 OUT5 OUT4 OUT3 OUT2 OUT1
ext=1
Notes
23. Trim Set bit indicates (0 = untrimmed, 1 = trimmed)
24. VCAL Status bit indicates when internal or external supply is used. VCAL Bit = 0 indicates external, VCAL Bit = 1indicates internal.
25. Reset Bit indicates the device has performed a POR.
33800
Analog Integrated Circuit Device Data
Freescale Semiconductor
29
FREESCALE [ Freescale ]
