CHAPTER
TWENTYFOUR
LEMONDROP BRING UP
Board draws approximately 24mA from +3V3 when power is applied. This seems a bit high, but may be expected if not
all parts are capable of low-power mode, or aren’t configured for low power at power-on. I need to review the schematic
and datasheets and see what can be done.
When I put my finger on the MAX2837, current consumption goes up. This suggests there may be floating nodes in
that region of the circuit.
24.1 Si5351 I2C
Attached crystal is 25MHz. For now, I’m assuming 10pF “internal load capacitance” is good enough to get the crystal
oscillating. The crystal datasheet should be reviewed and measurements made. ..
Be sure to reference Silicon Labs application note 619 (AN619). The datasheet is a terrible mess (typos and lack of
some details). AN619 appears to be less of a mess, on the whole. And as a bonus, AN619 has PDF bookmarks for
each register.
24.1.1 Connections
• Bus Pirate GND to P7 pin 1
• Bus Pirate +3V3 to P7 pin 2 (through multimeter set to 200mA range)
• Bus Pirate CLK to P7 pin 3
• Bus Pirate MOSI to P7 pin 5
24.1.2 Bus Pirate I2C Initialization
# set mode
m
# I2C mode
4
# ~100kHz speed
3
# power supplies ON
W
# macro 1: 7-bit address search
(1)
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