322 PI3VDP612-A DP to DP and HDMI Source Application Note Table of Contents 1. Introduction............................................................................................................................... 2 2. Application details .................................................................................................................... 2 3. Schematic Diagram .................................................................................................................. 4 4. Layout Consideration ............................................................................................................... 6 Page 1 of 6 AN322 Pericom Semiconductor Corp. www.pericom.com 11/4/2011 Rev 1.0 322 1. Introduction Pericom’s PI3VDP612-A mux/demux is targeted for next generation digital video signals. This device can be used to connect a DisplayPort (DP) source to two independent DP sinks or to connect two DP sources to a single DP display. Application note explains how to use the PI3VDP612-A to connect to a Dual Mode DP source signal to drive one Dual Mode DP port and one HDMI port on PC source application. Figure 1 illustrates this application. DP PC - Source Application Dual Mode DP Port Dual Mode DP Source PI3VDP612-A HDMI Port Figure 1: Application Diagram 2. DC Source Application The system needs to implement the following circuits for the application to work correctly: (1) HDMI Signal Level Shifter: This component is used to transform DP signal level to HDMI signal level. 499 pulldown resistor acts as a voltage divider in conjunction with the 50 +3.3V pull-up resistor on the HDMI sink device side to give a +3.0V DC offset voltage on the high speed HDMI lanes in order to meet HDMI signal level requirement. NMOS transistor connecting 499 resistor to GND is used to isolate the 499 connecting to GND when the system is powered down in order to meet HDMI compliance test specification’s TMDS-VOFF requirement. Only one NMOS is needed to connect all 8 pieces of 499 resistors pull down to GND to save cost and circuit form factor. (2) DDC Signal Level Shifter on HDMI port: This is used to level shift +3.3V interface DDC signal on the Dual Mode DP Source side to +5V interface on the HDMI port side using a single NMOS level shifter (3) HPD Signal Level Shifter on HDMI port: This is used to level shift +3.3V interface HPD signal on the Dual Mode DP Source side to +5V interface on the HDMI port side using a single NMOS level shifter Page 2 of 6 AN322 Pericom Semiconductor Corp. www.pericom.com 11/4/2011 Rev 1.0 322 Dual Mode DP Connector PI3VDP612-A High Speed Lanes Dual Mode DP Source High Speed Lanes AUX/DDC Port A HPD & CAB_DET AUX/DDC SEL High Speed Lanes DDC Port B HPD 499 R HDMI Level Shifter D +3.3V +5V G HDMI Connector S R G S R D DDC Level Shifter +3.3V R S DDC HPD +5V G R D HPD Level Shifter Figure 2: Application Circuit Page 3 of 6 AN322 Pericom Semiconductor Corp. www.pericom.com 11/4/2011 Rev 1.0 322 3. Schematic Diagram Figure 3: Application Schematics Page 4 of 6 AN322 Pericom Semiconductor Corp. www.pericom.com 11/4/2011 Rev 1.0 322 (1) Signal from Dual Mode DP Source High Speed Signal – 0.1uF AC-coupling capacitor is needed on the signal from Dual Mode DP Source AUX+/- or DDC Signal – In this design, we assume that AUX and DDC are multiplexed on the Dual Mode DP Source; hence, it is DC-coupled on these signals to PI3VDP612-A. It is recommended to check the Dual Mode DP Source to see whether it is matched to this assumption or not. Otherwise, circuit is needed to change accordingly HPD – If Hot Plug Detect (HPD) signal from Sink device is in logic High, it indicates that the selected port sink device is plugged in; Otherwise, selected port sink device is unplugged CAB_DET – If CAB_DET signal is in logic High, it indicates that the selected port sink device is HDMI/DVI device; If it is logic Low, it indicates that the selected port sink device is DP device. A 100kohm pull-up resistor is placed on CAB_DETB pin as port B is configured as HDMI port in this design SEL1/SEL2/AUX_SEL/HDMI_LS_SEL – These signals are control signals to select port and enable the HDMI level shifter, when SEL1/SEL2/AUX_SEL is logic Low port A is selected; otherwise, port B is selected. For this design, these signals could be tied together to control (2) Level Shifters SDA/SCL/HPD Level Shifter – It is used to level shift from +5V to +3.3V to interface with the Dual Mode DP signal level, 2N7002 NMOS could be used HDMI Level Shifter – It is used to transform from DP signal level to HDMI signal level. 499 pull-down resistor acts as a voltage divider in conjunction with the 50 +3.3V pull up resistor on the HDMI sink device side to give a +3.0V DC offset voltage on the high speed HDMI lanes in order to meet HDMI signal level requirement. NMOS (2N7002) connecting from 499 resistor to GND is to isolate the 499 connecting to GND when the system is powered down in order to meet HDMI compliance test specification’s ID 7-3 TMDS-VOFF requirement. Only one NMOS is needed to connect all 8 pieces of 499 resistors pull down to GND to save cost and circuit form factor (3) Power Supply Decoupling Four 0.1uF and one 1uF capacitors are recommended for PI3VDP612-A. 0.1uF capacitors should be placed as closed to the VDD pins and should be distributed evenly to all VDD pins (4) DP to HDMI pin mapping According to the DP interoperability guideline, the following DP Source Device to HDMI pin mapping is needed to follow: DP Pins Main Link Lane 0 Main Link Lane 1 Main Link Lane 2 Main Link Lane 3 AUX CH+ AUX CHHPD Pin 13 Pin 14 HDMI/DVI Pins Channel 2 Channel 1 Channel 0 Channel CLK DDC Clock (SCL) DDC Data (SDA) HPD Cable Adaptor Detect (Optional) CEC Table 1: DP to HDMI Pin Mapping Page 5 of 6 AN322 Pericom Semiconductor Corp. www.pericom.com 11/4/2011 Rev 1.0 322 4. Layout Consideration (1) Power Supply Decoupling Capacitors The Power Supply Decoupling Capacitors should be placed as close to the VDD pins of PI3VDP612-A as possible in order to reduce the trace inductance to enhance the decoupling performance. And it should be distributed evenly to all VDD pins (2) Via on thermal pad Via(s) is recommended to be placed on the thermal pad layout in order to have good electrical and thermal connection to GND (3) 499ohm resistors Traces connecting from the main link of HDMI port to 499ohm resistors should be minimized as these traces act like a stub, which affect the trace impedance at high frequency Figure 4: HDMI Level Shifter 499ohm Resistor Trace Consideration in Layout Page 6 of 6 AN322 Pericom Semiconductor Corp. www.pericom.com 11/4/2011 Rev 1.0