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
Table 6. Load Resistance Measurement Select
Bits 9876
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
MUX Select
Normal Operation
• 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.
VDSNS1 to REXT, VDSNS2 to Diff-Amp +
VDSNS2 to REXT, VDSNS1 to Diff-Amp +
VDSNS3 to REXT, VDSNS4 to Diff-Amp +
VDSNS4 to REXT, VDSNS3 to Diff-Amp +
VDSNS5 to REXT, VDSNS6 to Diff-Amp +
VDSNS6 to REXT, VDSNS5 to Diff-Amp +
Normal Operation
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.
Normal Operation
Normal Operation
GATE DRIVE ON/OFF COMMAND
VDSNS2 to REXT, VDSNS1 to Diff-Amp +
VDSNS3 to REXT, VDSNS1 to Diff-Amp +
VDSNS4 to REXT, VDSNS1 to Diff-Amp +
VDSNS5 to REXT, VDSNS1 to Diff-Amp +
VDSNS6 to REXT, VDSNS1 to Diff-Amp +
Normal Operation
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
33800
Analog Integrated Circuit Device Data
Freescale Semiconductor
21
FREESCALE [ Freescale ]
