NXP Semiconductors PCA9955BTW-ARD User manual

UM11761
PCA9955BTW-ARD evaluation board
Rev. 1.0 — 18 March 2022 User manual
Document information
Information Content
Keywords PCA9955B, I2C-bus, LED, LED driver, Arduino port, EVK
Abstract The “PCA9955BTW-ARD” evaluation board is a daughterboard equipped
with Arduino port, designated for easy test and design of PCA9955B IC, 16-
channel Fm+ I2C-bus 57 mA / 20 V constant current LED driver. The board is
fully compliant with IMXRT1050 EVK, LPCXpresso55S69 and i.MX 8M Mini
LPDDR4 EVK, including GUI software control. The board can be attached to
any device equipped with Arduino port.

NXP Semiconductors UM11761
PCA9955BTW-ARD evaluation board
Rev Date Description
v1.0 20220318 Initial version
Revision history
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PCA9955BTW-ARD evaluation board
IMPORTANT NOTICE
For engineering development or evaluation purposes only
NXP provides the product under the following conditions:
This evaluation kit is for use of ENGINEERING DEVELOPMENT OR
EVALUATION PURPOSES ONLY. It is provided as a sample IC pre-
soldered to a printed-circuit board to make it easier to access inputs,
outputs and supply terminals. This evaluation board may be used with any
development system or other source of I/O signals by connecting it to the
host MCU computer board via off-the-shelf cables. This evaluation board
is not a Reference Design and is not intended to represent a final design
recommendation for any particular application. Final device in an application
heavily depends on proper printed-circuit board layout and heat sinking
design as well as attention to supply filtering, transient suppression, and I/O
signal quality.
The product provided may not be complete in terms of required design,
marketing, and or manufacturing related protective considerations, including
product safety measures typically found in the end device incorporating the
product. Due to the open construction of the product, it is the responsibility of
the user to take all appropriate precautions for electric discharge. In order to
minimize risks associated with the customers’ applications, adequate design
and operating safeguards must be provided by the customer to minimize
inherent or procedural hazards. For any safety concerns, contact NXP sales
and technical support services.
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PCA9955BTW-ARD evaluation board
1 Introduction
This document describes the PCA9955BTW-ARD evaluation board, which is built around
the PCA9955B, a 16-channel Fm+ I2C-bus 57 mA/20V constant current LED driver
produced by NXP Semiconductors. The board works as a daughterboard which can
be connected through an Arduino port to various Arduino compatible (including original
Arduino Uno R3) boards. The board is intended to test and measure the characteristics
of the PCA9955B Device Under Test (DUT).
The PCA9955BTW-ARD communicates through the Arduino port with the motherboard
(EVK) via the bidirectional Fm+ (1 MHz) I2C-bus. Alongside the I2C-bus, three additional
lines allow the motherboard to control the DUT through the same Arduino port.
The PCA9959BTW-ARD board is equipped with a pair of dedicated connectors which
allow to interconnect more boards in a chain architecture.
The PCA9955BTW-ARD board can be powered in two ways: from the EVK through
the Arduino port, or externally through a dedicated power connector, located on the
daughterboard.
The board contains three RGB LEDs and seven white LEDs allocated to all sixteen
outputs of the PCA9955B DUT. The board also contains jumpers and connectors that
allows users to disconnect the on-board LEDs, to perform short tests, and to connect
external LEDs to the driver outputs.
Additionally, the daughterboard has software support and a graphical user interface
(Windows platform) for the following NXP evaluation boards: IMXRT1050 EVK Board,
LPCXpresso55S69 Development Board and i.MX 8M Mini LPDDR4 EVK Board.
2 Finding kit resources and information on the NXP web site
NXP Semiconductors provides online resources for evaluation board and its supported
device(s) on http://www.nxp.com.
The information page for PCA9955BTW-ARD evaluation board is at http://www.nxp.com/
PCA9955BTW-ARD. The information page provides overview information,
documentation, software and tools, parametrics, ordering information and a Getting
Started tab. The Getting Started tab provides quick-reference information applicable
to using the PCA9955BTW-ARD evaluation board, including the downloadable assets
referenced in this document.
2.1 Collaborate in the NXP community
The NXP community is for sharing ideas and tips, ask and answer technical questions,
and receive input on just about any embedded design topic.
The NXP community is at http://community.nxp.com.
3 Getting ready
Working with the PCA9955BTW-ARD requires the kit contents, additional hardware, and
a Windows PC workstation with installed software.
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PCA9955BTW-ARD evaluation board
3.1 Kit contents
•Assembled and tested evaluation board in an antistatic bag
•Quick Start Guide
3.2 Assumptions
Familiarity with the I2C bus is helpful but not required.
3.3 Static handling requirements
CAUTION
This device is sensitive to ElectroStatic Discharge (ESD). Therefore care
should be taken during transport and handling. You must use a ground strap
or touch the PC case or other grounded source before unpacking or handling
the hardware.
3.4 Minimum system requirements
This evaluation board requires a Windows PC workstation. Meeting these minimum
specifications should produce great results when working with this evaluation board.
•Computer with Windows 10
•One USB port (either 3.0 or 2.0 or 1.1 compatible)
•One of three EVK boards (MIMXRT1050-EVK, LPC55S69-EVK, 8MMINILPD4-EVK)
along with the associated firmware / GUI software
•USB cable for power and data connection between PC and EVK board (if not included
in the EVK package)
4 Getting to know the hardware
4.1 PCA9955BTW-ARD features
•Multiple board connection in chain architecture
•Switch for output current limit up to 20 mA / 50 mA
•Equipped with Arduino Uno R3 port for direct connection with Arduino devices
•Combined power from Arduino or external source
•On-board jumpers for LED connection, and short tests
•On-board connectors for external LEDs
•Fully compliant with IMXRT1050 EVK board, including GUI (Windows 10)
•Fully compliant with LPCXpresso55S69 development board, including GUI (Windows
10)
•Compliant with i.MX Mini LPDDR4 EVK board, including GUI (Windows 10)
Note: For i.MX Mini LPDDR4 EVK Board is necessary to use IMX8MMINI-IARD
interposer board between the EVK and PCA9955BTW-ARD daughterboard (see
IMX8MMINI-IARD User Manual).
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NXP Semiconductors UM11761
PCA9955BTW-ARD evaluation board
4.2 Kit featured components
Figure 1 identifies the main components on the board. The main elements are called
out in the picture. The DUT (U2) is located in the center of the board. The on-board
LEDs connected to the driver are placed around the PCA9955B IC. The Arduino port
connectors (J5, J6, J35, J36) are located on the bottom side of the board.
Figure 1. PCA9955BTW-ARD arduino board: top view (up) and bottom view (down)
4.3 Schematic diagram
The schematic diagram of PCA9955BTW-ARD is available at URL: http://www.nxp.com/
PCA9955BTW-ARD.
4.4 General description
Figure 2 shows the block diagram of PCA9955BTW-ARD daughterboard. The block
diagram includes the Arduino interface (J5, J6, J35, J36), the expansion connectors for
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NXP Semiconductors UM11761
PCA9955BTW-ARD evaluation board
chain configuration (J45 / J89, see Section 4.7), and the on-board LEDs, connected to
the output of the DUT (U2).
Figure 2. PCA9955BTW-ARD block diagram
The PCA9959B is controlled through an I2C interface. The motherboard (EVK) uses an
I2C-bus to control the PCA9955BTW-ARD daughterboard through the Arduino port. The
blue lines in the drawing refer to the I2C-bus. From the Arduino connector J35, the I2C
lines are connected to the SDA / SCL pins of the DUT (U2, pin 26, and 27), and to the
expansion connectors J45 and J89. For more details, see the schematic diagram of the
PCA9955BTW-ARD board.
The target address of the PCA9955B can be configured for 125 different target
addresses, by unique combination of five states to three address inputs of the IC (U2, pin
2, 3, and 4). For details, see PCA9955B datasheet (NXP Semiconductors). The jumper
headers J86, J87 and J88, allow to select only 27 from 125 possible addresses. Table 1
depicts the target address depending on the position of the address jumpers. Note that
the default selected address is BCh.
J88 position J87 position J86 position I2C target address (HEX)
1-2 1-2 1-2 BCh (default)
1-2 1-2 2-3 B8h
1-2 1-2 OFF BAh
1-2 2-3 1-2 A8h
1-2 2-3 2-3 A4h
1-2 2-3 OFF A6h
1-2 OFF 1-2 B2h
1-2 OFF 2-3 AEh
Table 1. I2C target address chart
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NXP Semiconductors UM11761
PCA9955BTW-ARD evaluation board
J88 position J87 position J86 position I2C target address (HEX)
1-2 OFF OFF B0h
2-3 1-2 1-2 58h
2-3 1-2 2-3 54h
2-3 1-2 OFF 56h
2-3 2-3 1-2 44h
2-3 2-3 2-3 40h
2-3 2-3 OFF 42h
2-3 OFF 1-2 4Eh
2-3 OFF 2-3 4Ah
2-3 OFF OFF 4Ch
OFF 1-2 1-2 8Ah
OFF 1-2 2-3 86h
OFF 1-2 OFF 88h
OFF 2-3 1-2 76h
OFF 2-3 2-3 72h
OFF 2-3 OFF 74h
OFF OFF 1-2 80h
OFF OFF 2-3 7Ch
OFF OFF OFF 7Eh
Table 1. I2C target address chart...continued
Alongside the I2C-bus, the circuit contains three control lines: the OE, RESET, and
MUX (REXT). In the block diagram the control lines are drawn with purple. The OE and
RESET lines control the corresponding OE and RESET inputs of the PCA9955B IC (U2,
pin 5, and 25). Driving low the OE input, enables all sixteen outputs of the LED driver.
Driving low the RESET input, sets the internal registers of PCA9959B to their default
state. For more details, see PCA9955B datasheet (NXP Semiconductors).
The limit current for each output of PCA9955B is set by a resistor connected between
REXT (U2, pin 1) and ground. The switch U5 allows to select two values for current limit:
20 mA (U1 – OFF), and 50 mA (U1 – ON). The state of U1 switch is controlled through
the MUX (REXT) line.
All control lines (purple color in the block diagram picture) are connected to the
expansion connectors J45 and J89. For more details, see the schematic diagram of the
PCA9955BTW-ARD board.
The PCA995B features sixteen LED drivers (PWM controlled, current sink sources).
Three RGB LEDs are allocated to the first outputs (LED0 to LED8). The outputs LED9
to LED15 drives white LEDs. The LEDs can be disconnected from the IC outputs with
jumpers.
The RGB LED D16 has jumpers connected in parallel for short testing. The jumpers J76
to J81 allows the user to redirect the corresponding output lines of D16 and D17 RGB
LEDs from the on-board LEDs to the RGB LED external connectors (J21 and J26). Using
the connectors, the user can easily attach external LEDs for testing. In the same manner,
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PCA9955BTW-ARD evaluation board
the corresponding lines of white LEDs D9 and D10 can be redirected with J82 and J83
jumpers to white LED external connectors J23 and J25.
4.5 Arduino port
J5, J6, J35, and J36 are the mated pin headers of Arduino Uno R3 connectors, having
the same electrical function and placed on the board, so that the daughterboard can
be directly inserted in the Arduino port. The daughterboard uses only five signal lines.
Table 1 lists the pin chart of connectors, and the lines used in the circuit (see also the
SPF-46660_A1.pdf schematic file):
Ref Des # Arduino label PCA9955BTW-ARD function
1 NC Not used
2 IOREF Not used
3 RESET Not used
4 3.3V Not used
5 5V Power supply
6 GND Power supply return
7 GND Power supply return
J6 (Power)
8 Vin Not used
1 A0 Not used
2 A1 Not used
3 A2 Not used
4 A3 Not used
5 A4 / SDA I2C – SDA
J35 (analog, digital, I2C)
6 A5 / SCL I2C – SCL
1 D0 / RX Not used
2 D1 / TX Not used
3 D2 Not used
4 D3 / PWM Not used
5 D4 Not used
6 D5 / PWM Not used
7 D6 / PWM Not used
J5 (digital, UART, PWM)
8 D7 Not used
1 D8 RESET
2 D9 / PWM OE
3 D10 / SS / PWM MUX (REXT)
4 D11 / MOSI / PWM Not used
5 D12 / MISO Not used
J36 (mixed)
6 D13 / SCK Not used
Table 2. The pin chart of Arduino connectors and their usage
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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.
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