LX7720 Daughter Board User's Manual
June 2020
LX7720 Daughter Board rev 2.1
8
© 2020 Microsemi Corporation
Fitment
Selection
See Section
Notes
Link 1 to 2
Enables the LC filter comprising L1, C29, C30, and R6 between LX7720
DMOD_OUT_N pin 44 and DMOD_OUT_P pin 46 outputs. The filter shapes the
PWM output waveform to drive a resolver or LVDT primary
J6
Open
The LX7720 DMOD_OUT_N pin 44 and DMOD_OUT_P pin 46 outputs remain
unfiltered PWM
Resolver/LVDT
driver filter
Link 1 to 2
Couple the filtered resolver/LVDT driver outputs LX7720 DMOD_OUT_N pin 44
and DMOD_OUT_P pin 46 to LX7720 ADC3_N pin 36 and ADC3_P pin 37 for
measurement of the drive amplitude and fault detection
Resolver/LVDT
driver
measurement
J7,
J8
Open
LX7720 ADC3_N pin 36 and ADC3_P pin 37 are available for other purposes
ADC3 inputs
J10
HPC1-FMC
connector
HPC1-FMC connector to RTG4 Development Kit board. The same signals are
provided to this FMC connector and the 40-pin header J20, so connect to one or
the other but not both
RTG4 interface
J13
DMOD
outputs
Resolver/LVDT driver outputs LX7720 DMOD_OUT_N pin 44 and DMOD_OUT_P
pin 46 outputs. If J6 is linked to enable the on-board LC filter, then the filtered
drive outputs are available at J13 pins 2 and 3. If J6 is open, then the raw PWM
drive outputs are available at J13 pins 1 and 3
Resolver/LVDT
driver outputs
J14
ADC Inputs
The 3 differential inputs {ADC1_P, ADC1_N}, {ADC2_P, ADC2_N}, and {ADC3_P,
ADC3_N} feed the ADC1, ADC2, and ADC3 sigma delta modulators
ADC1 to ADC3
J15
BLI Inputs
BLI1 to BLI6 inputs, VCC, and GND. BLI_TH is set to VCC/2 by R4 & R5
BLI inputs
Link 1 to 2
Fit when not using J16 to measure VDD (nominally 3.3V) supply current
Normal usage
Shunt resistor
or ammeter
Replace link with current measuring device if desired for VDD from regulator U4
Measure V
current
J16
Open
External VDD supply in the range 2.75V to 3.6V at connector J18
External 2.75V
to 3.6V VDD
Link 1 to 2
Fit when not using J17 to measure VCC (nominally 5V) supply current from
regulator U10
Normal usage
Shunt resistor
or ammeter
Replace link with current measuring device if desired for VCC from regulator U10
Measure VCC
current
J17
Open
External VCC supply in the range 4.5V to 5.5V at connector J30
External 4.5V
to 5.5V VCC
J18
Pin 1: VDD
Pin 2: GND
When using external VDD supply in the range 2.75V to 3.6V, apply the VDD
supply to J18, and ensure that J16 is open so that regulator U4 is not back-driven
External 2.75V
to 3.6V VDD
Link 2 to 1
VDD supply is 3.3V from FMC connector J10 pins C39, D32, D36, D38, and D40.
J16 also needs to be linked. Do not apply an external VDD supply to either J18 or
J20 pin 30 with an RTG4 Development Kit board plugged into J10, because this
will back-drive the RTG4 Development Kit's 3.3V supply
VDD = 3.3V
from J10
Link 2 to 3
VDD supply is from 3.3V regulator U4. Configure J36 for desired U4 voltage
source also
VDD = internal
3.3V
J19
Open
VDD supply is 2.75V to 3.6V from either 40-pin header J20 pin 30 or from J18.
Ensure that J16 is also open so that regulator U4 or an RTG4 Development Kit
board plugged into J10 are not back-driven
2.75V to 3.6V
VDD from J20
pin 30 or J18
J20
Controller
connector
40 pin header to external MCU or FPGA controller. The same signals are
provided to this 40-pin header and the FMC connector J10, so connect to J10 or
to J20, but not to both
Controller
interface
J26
SMA socket External 24MHz to 32MHz MOD_CLK. R136 = 33
Ω
must be fitted
4.7, page 13 MOD_CLK
J27
SMA socket External 100kHz to 300kHz CP_CLK. R135 = 33
Ω
must be fitted
4.8, page 13 Charge pump
J30
Pin 1: VCC
Pin 2: GND
When using external VCC supply in the range 4.5V to 5.5V, apply the VCC supply
to J30, and ensure that J17 is open so that regulator U10 is not back-driven
External 4.5V
to 5.5V VCC
J31
Pin 1: VGS
Pin 2: GND
When using external VGS supply in the range 10V to 18V, apply the VGS supply
to J31, and ensure that link J32 is open so that regulator U3 is not back-driven
External 10V to
18V VGS
Link 1 to 2
Fit when using internal 15V supply for VGS, and not using J32 to measure 15V
supply current
Normal usage
Shunt resistor
or ammeter
Replace link with current measuring device if desired when using internal 15V
supply for VGS
Measure VGS
current
J32
Open
Omit link when using external VGS supply in the range 10V to 18V at connector
J31
External 10V to
18V VGS
Link 2 to 1
VCC (5V) regulator U10 source is the VGS rail selected by J32
Normal usage
Link 2 to 3
VCC (5V) regulator U10 source is 12V from FMC connector J10 pins C35 and
C37
RTG4 source
J35
Open
VCC (5V) regulator U10 source is unpowered. Provide an external 4.5V to 5.5V at
connector J30, and ensure that link J17 is open so that regulator U10 is not back-
driven
External 4.5V
to 5.5V VCC
