33800 datasheet(21/39 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33800

FUNCTIONAL DEVICE OPERATION

LOGIC COMMANDS AND REGISTERS

• Off State Open Load Detect

• On State Short Circuit Detect

• Programmable Drain Threshold and Timer for Short Fault

Detection

• Load Resistance Measurement

Each pre-driver is capable of detecting an open load in the

off state and shorted load in the on state. All faults are

reported through SPI communication. For open load

detection, a resistor is placed between the drain sense pin

and source sense pin of the IC. An open load fault is reported

when the drain voltage is less than the 2.5V threshold. A

shorted load fault is reported when the drain voltage is

greater than the programmed threshold voltage.

Programming of the drain short fault threshold voltage is

done through SPI commands provided in Table 7.

Bits 6 through 9 are used to perform the load resistance

measurement function as described in the Gate Drive On/Off

Command section below.

GATE DRIVE ON/OFF COMMAND

The GD ON/OFF Command provides control bits for two

functions:

• On/Off control of the GDx outputs.

• Load Resistance measurement function.

On/Off control bit 0 through bit 5 control gate drive outputs

GD1 through GD6 respectively. Setting the bit to logic1 will

enable the gate drive to the external MOSFET. Setting the bit

to logic 0 will actively pull the gate to ground.

GD ON/OFF Command bits 6 through 9 control the load

measurement feature. The gate drive pre-drivers are

selected in matched pairs. Selecting a load resistance

measurement disables a specified output pair and performs

the resistance measurement using the defined pair. All other

outputs will operate as programmed. Resistance is measured

by passing a known current through the load and by

measuring the voltage across it. The resistor placed on the

REXT pin determines the current through the load during

measurement. The voltage output on the LRFDBK pin is the

differential load voltage with the defined current through it.

From the two parameters, the load resistance may be

calculated. Table 6 illustrates the load diagnostic multiplex

function.

PWM PIN ENABLE COMMAND

The PWM Pin Enable Command provides control bits for

two functions:

• Enable or Disable of PWM input pins.

• Enable or Disable of the internal PWM controller for GD1

through GD6.

PWM pin Enable bit 0 through bit 5 enable or disable the

PWM1 through PWM6 input pins respectively. A logic 0 in the

SPI word will enable the PWM input pin, while logic 1 in the

SPI word will disable the PWM input pin. Default state is with

the PWM input pin enabled. With the PWM input pin disabled,

the AND/OR function is also disabled and control is achieved

through the Gate Drive ON/OFF command or the internal

PWM controller.

AND/OR COMMAND

The AND/OR Command provides control bits for two

functions:

• Determines AND/OR relation between ON/OFF SPI bit

and PWM input pin.

• Enable or Disable of the internal PWM controller for G1

through GD6.

The AND/OR command describes the condition by which

the PWM input pin controls the output driver. A logic[0] in the

AND/OR register will OR the PWM input pin with the

respective bit in the ON/OFF register. Likewise, a logic[1] in

Table 6. Load Resistance Measurement Select

Bits 9876

MUX Select

0000

Normal Operation

0001

VDSNS1 to REXT, VDSNS2 to Diff-Amp +

0010

VDSNS2 to REXT, VDSNS1 to Diff-Amp +

0011

VDSNS3 to REXT, VDSNS4 to Diff-Amp +

0100

VDSNS4 to REXT, VDSNS3 to Diff-Amp +

0101

VDSNS5 to REXT, VDSNS6 to Diff-Amp +

0110

VDSNS6 to REXT, VDSNS5 to Diff-Amp +

0111

Normal Operation

1000

Normal Operation

1001

Normal Operation

1010

VDSNS2 to REXT, VDSNS1 to Diff-Amp +

1011

VDSNS3 to REXT, VDSNS1 to Diff-Amp +

1100

VDSNS4 to REXT, VDSNS1 to Diff-Amp +

1101

VDSNS5 to REXT, VDSNS1 to Diff-Amp +

1110

VDSNS6 to REXT, VDSNS1 to Diff-Amp +

1111

Normal Operation

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