Analog Integrated Circuit Device Data

Freescale Semiconductor

29

33800

FUNCTIONAL DEVICE OPERATION

LOGIC COMMANDS AND REGISTERS

greater than 0.0mA. Commands outside of this command

range will automatically lock out dither.

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. 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.

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

Command Bits

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

CCD2 Command Address

Diag

Pull-

up

DTHR

DIS

9 BIT DAC Command Data

CCD2 Control

0 = Pull-down Current Source

1 = Pull-up Current Source

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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

Next SO Response (Message 2)

0 = No Fault, 1 = Fault

OvrVlt

,TLim

or

CAL

Flt

Reset Trim

Set (23)

VCAL

Status

int=0

ext=1

Open

Fault

CCD2

Short

Fault

CCD2

Open

Fault

CCD1

Short

Fault

CCD1

Fault

Status

OUT8

Fault

Status

OUT7

Fault

Status

OUT6

Fault

Status

OUT5

Fault

Status

OUT4

Fault

Status

OUT3

Fault

Status

OUT2

Fault

Status

OUT1

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.