NXP Semiconductors PCA9955BTW-ARD, Руководство пользователя, Страница: 10 / 38

NXP Semiconductors
UM11761
PCA9955BTW-ARD evaluation board
Ref Des # Arduino label PCA9955BTW-ARD function
7 GND Power supply return
8 AREF Not used
9 A4 / SDA Not used
10 A5 / SCL Not used
Table 2. The pin chart of Arduino connectors and their usage
...continued
The circuit is supplied with 5 V from Arduino port through J6 and J36. Pin 5 of J6 is 5 V
power supply, while pin 6 and 7 of J6 and pin 7 of J36 represent the power supply return
(ground).
4.6 Power distribution
The electrical circuit of PCA9955BTW-ARD is supplied from 5 V and 3.3 V power rails.
The 5 V power supply can be provided from two sources: from the EVK through the
Arduino port, and externally through the power connector J85. The jumper header J8
selects the 5 V source. The 3.3 V rail is obtained with the LDO regulator U5, from the 5 V
rail. The necessary current for one daughterboard when all LEDs are ON is 800 mA (I
limit set to 50 mA). If one board is used, there is no limitation or restriction regarding the
5 V power source. If more boards are used in a chain configuration (see Section 4.7 ),
when the power is supplied by EVK through the Arduino port, due to current limitation,
the number of boards connected in the chain is limited. The limitation depends on the
type of EVK being used and the current rating of the Arduino connectors. The current
limitation as a function of EVK is as follows:
• IMXRT1050 EVK:
–
EVK powered from USB: limited by the current rating of the USB connector –
maximum 3 boards;
– EVK powered from power barrel connector (J2): limited by power rating of Arduino /
Fuji connectors – maximum 4 boards;
• LPCXpresso55S69 EVK: limited by the current rating of the USB connector – maximum
3 boards;
• i.MX LPDDR4 EVK: limited by the current delivered by the EVK power supply –
maximum 3 boards;
When the 5 V power is provided externally (through J85), there is no power limitation,
regarding the number of boards used in the chain. The on-board LED D2 is 3.3 V rail
indicator, and D3 is 5 V external indicator.
4.7 Chain configuration
The expansion connectors J45 and J89 allow to interconnect more boards in a chain
configuration, as is shown in Figure 3 . J45 is labeled as “CHAIN – LEFT”, while J89 is
“CHAIN – RIGHT”. The mains are given upon their position on the daughterboard (J45 is
placed in the left side, while J89 in placed in the right side of the board). Note that, when
more boards are used in a chain configuration, each board must set its individual target
address. When the boards are supplied from the EVK, the number of board are limited
due to power consumption of the boards. See Section 4.6 for more details. To overcome
this limitation, use an external power supply. Table 3 depicts the pin chart of expansion
connectors, J45 and J89.
UM11761 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2022. All rights reserved.
User manual Rev. 1.0 — 18 March 2022
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