NXP constant-current LED controller PCA9922 for LED video walls Maximize the impact of LED video walls while cutting costs This constant-current LED driver extends advertising budgets by maximizing the impact of LED video walls while reducing overall cost. It is a pin-to-pin and functionally equivalent 5-V alternative to the ST2221A and STP08CDC596. Key features } 8 LED driver outputs with low-side, constant-current control } 25-MHz serial interface } Maximum current from 15 to 60 mA for all 8 output channels (set by external resistor) } Constant current matching at 25 °C, VDD = 5.0 V : - Bit-to-bit: ±6 % - Chip-to-chip: ±10 % } Gradual turn-on/turn-off output to limit EMI } Error detection mode for line open, output short to ground, LED open, and LED short } Operating voltage: 3.3 to 5.5 V } ESD protection exceeds 2000 V HBM and 1000 V CDM } Package options: DIP16, TSSOP16 and HVQFN20 Key applications } Full-color, multi-color, and monochrome LED signs } LED billboard displays } Colorful LED video walls } Traffic display signs } Transportation and commercial LED signs } Scrolling message boards The NXP PCA9922 is a single-chip solution for LED displaydriving that is optimized for LED video walls, video billboards, and digital signage. It is a low-cost, 5-V alternative that is pin-topin compatible with and functionally equivalent to the SS2221A and STP08CDC596 (exception: error data is inverted). The PCA9922 integrates a shift register, accompanying data latches, eight NPN constant-current sink drivers, and an LED output error detection circuit. The shift register and latches allow direct interfacing with microprocessor-based systems. With a 5-V logic supply, typical serial data-input rates can reach up to 25 MHz. A serial data output permits cascading between multiple devices in applications requiring additional drive lines. Open LED connections can be detected and signaled back to the host microprocessor through the SERIAL DATA OUT pin. The brightness of an LED sign is proportional to the current flowing through the LEDs. The PCA9922 is designed specifically to address the variables that affect the brightness consistency of an LED sign. Selection of the Rext (current setting resistor) value determines the maximum current to be maintained by the outputs. Typical Application The PCA9922 in a typical multi-device architecture VLED = 3 V ^ 4 V + VCE VDD scan 5V C 10 MF R OE 3.3 V to 5.5 V LED0 LED1 LED2 LED7 CLK LE VSS SDO PCA9922 VO VI VO VI LED7 R_EXT VSS SDO to next stage OE PWM OR BLANKING INPUT MICROCONTROLLER LE LED0 SDI VDD PCA9922 R_EXT SDI LED3 CPU CLK OE CLK LE LED0 PCA9922 LED7 SDI SDO from last stage R_EXT VSS SDO 002aad312 002aad504 PCA9922 block diagram LED0 LED1 LED7 VDD ERROR DETECT CURRENT REGULATOR R_EXT VDD PCA9922 OE OUTPUT ENABLE LE 8¾ DATA LATCH AUTO SHUTDOWN AND AUTO POWER-UP VSS SDI 8¾ SHIFT REGISTER SDO CLK VSS ERROR CONTROL 002aad311 Ordering Information Type number Package Number of pins ST Type Number PCA9922N DIP16 16 STP08CDC596B1 Silicon Touch Type Number ST2221A PCA9922PW TSSOP16 16 STP08CDC596TTR ST2221A PCA9922BS HVQFN20 20 - - www.nxp.com/i2clogic www.nxp.com © 2009 NXP B.V. All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. Date of release: February 2009 The information presented in this document does not form part of any quotation or contract, is believed to be accurate and Document order number : 9397 750 16670 reliable and may be changed without notice. No liability will be accepted by the publisher for any consequence of its use. Printed in the Netherlands Publication thereof does not convey nor imply any license under patent- or other industrial or intellectual property rights.