ZLAN-414 Footprint Compatibility of Microsemi Clock Buffers with Competitors Application Note December 2012 1.0 Introduction In order to help customers quickly integrate the new Microsemi clock distribution buffers into existing designs, selected clock buffer devices are footprint compatible with other devices. This application note lists the compatible parts and highlights the differences between the Microsemi devices and their footprint compatible parts. The devices and their industry counterparts are listed here: Microsemi Device Industry Counterpart ZL40203 SY58021U ZL40203 ADCLK944 ZL40211 SY89837U Table 1 - Compatible Devices 2.0 Footprint Compatibility of ZL40203 with Micrel SY58021U The ZL40203 has been designed to be footprint compatible with the Micrel SY58021U. The following table shows the similarity of the pin map and also highlights the slight differences. Pin ZL40203 Pin Name SY58021U Pin Name 1 clk_p IN 2 vt VT 3 ctrl VREF-AC 4 clk_n /IN 5 gnd GND 6 out3_n /Q3 7 out3_p Q3 8 vdd VCC 9 out2_n /Q2 10 out2_p Q2 11 out1_n /Q1 12 out1_p Q1 13 vdd VCC 14 out0_n /Q0 15 out0_p Q0 16 gnd GND Comment See differences Table 2 - Pin Commonality between ZL40203 and SY58021U 1 Microsemi Corporation Copyright 2012, Microsemi Corporation. All Rights Reserved. ZLAN-414 Application Note For a DC coupled LVPECL input on pin 1 and 4, the SY58021U and the ZL40203 should be configured identically as shown in Figure 1. Note that for the ZL40203, pin 3 (ctrl) is a control pin which engages the internal biasing network when asserted. It is internally pulled to gnd (i.e logic 0) when unconnected. This pin could optionally be pulled down externally. Pin 3 (VREF-AC) on SY58021U is a voltage reference and should be left floating. SY58021U ZL40203 IN clk_p LVPECL LVPECL /IN clk_n C C VT VCC vt Vdd Rpd NC Rpd VREF-AC NC For VCC=3.3V, Rpd=50 ohm For VCC=2.5V, Rpd=19 ohm ctrl C is optional but improves common mode rejection. For Vdd=3.3V, Rpd=50 ohm For Vdd=2.5V, Rpd=19 ohm Figure 1 - DC-Coupled LVPECL input For an AC-coupled LVPECL input, the devices should be configured as shown in Figure 2. ZL40203 SY58021U clk_p IN LVPECL LVPECL clk_n /IN C C VCC Vdd VT Rs vt Rs VREF-AC ctrl Rm Rm Depopulate Rm Rs = 0 ohm Depopulate Rs C is optional Rm = 0 ohm Figure 2 - AC-coupled LVPECL input 2 Microsemi Corporation ZLAN-414 Application Note For a DC-coupled LVDS input signal, the devices should be configured identically as shown in Figure 3. Note again that the ctrl pin on the ZL40203 is pulled down internally. SY58021U ZL40203 IN clk_p LVDS LVDS /IN clk_n NC VT NC vt NC VREF-AC NC ctrl Figure 3 - DC-coupled LVDS input For AC-coupled LVDS, the devices should be configured as shown in Figure 4. SY58021U ZL40203 IN LVDS clk_p Rl LVDS Rl /IN clk_n C C VT VCC vt Vdd Rs Rs VREF-AC ctrl Rm Rm Depopulate Rs C is optional Rm = 0 ohm For Vdd=3.3V, Rl = 900 ohm For Vdd=2.5V, Rl = 600 ohm Depopulate Rm Rs = 0 ohm For VCC=3.3V, Rl = 900 ohm For VCC=2.5V, Rl = 600 ohm Figure 4 - AC-Coupled LVDS input 3 Microsemi Corporation ZLAN-414 3.0 Application Note Footprint Compatibility of ZL40203 with ADI ADCLK944 The ZL40203 has been designed to be footprint compatible with the ADI ADCLK944. The following table shows the similarity of the pin map and also highlights the slight differences. Pin ZL40203 Pin Name ADCL944 Pin Name 1 clk_p CLK 2 vt VT 3 ctrl VREF 4 clk_n CLK 5 gnd VEE 6 out3_n Q3 7 out3_p Q3 8 vdd VCC 9 out2_n Q2 10 out2_p Q2 11 out1_n Q1 12 out1_p Q1 13 vdd VCC 14 out0_n Q0 15 out0_p Q0 16 gnd VEE Comment See differences Table 3 - Pin Commonality between ZL40203 and ADCLK944 For a DC-coupled LVPECL input on pin 1 and 4, the ADCLK944 and the ZL40203 should be configured identically as shown in Figure 5. Note that for the ZL40203, pin 3 (ctrl) is a control pin which engages the internal biasing network when asserted. It is internally pulled to gnd (i.e logic 0) when unconnected. This pin could optionally be pulled down externally. Pin 3 (VREF) on ADCLK944 is a voltage reference and should be left floating. 4 Microsemi Corporation ZLAN-414 Application Note ADCLK944 ZL40203 CLK clk_p LVPECL LVPECL CLK clk_n C C VCC VT vt Vdd Rpd NC Rpd NC VREF For VCC=3.3V, Rpd=50 ohm For VCC=2.5V, Rpd=19 ohm ctrl C is optional but improves common mode rejection. For Vdd=3.3V, Rpd=50 ohm For Vdd=2.5V, Rpd=19 ohm Figure 5 - DC-coupled LVPECL input For an AC-coupled LVPECL input, the devices should be configured as shown in Figure 6. ZL40203 ADCLK944 clk_p CLK LVPECL LVPECL clk_n CLK C C VCC Vdd VT Rs vt Rs VREF ctrl Rm Rm Depopulate Rm Rs = 0 ohm Depopulate Rs C is optional Rm = 0 ohm Figure 6 - AC-coupled LVPECL input 5 Microsemi Corporation ZLAN-414 Application Note For a DC coupled LVDS input signal, the devices should be configured identically as shown in Figure 7. Note again that the ctrl pin on the ZL40203 is pulled down internally. ADCLK944 ZL40203 CLK clk_p LVDS LVDS CLK clk_n NC VT NC vt NC VREF NC ctrl Figure 7 - DC-coupled LVDS input For AC coupled LVDS, the devices should be configured as shown in Figure 8. ADCLK944 ZL40203 CLK LVDS clk_p Rl LVDS Rl CLK clk_n C C VT VCC vt Vdd Rs Rs ctrl VREF Rm Rm Depopulate Rs C is optional Rm = 0 ohm For Vdd=3.3V, Rl = 900 ohm For Vdd=2.5V, Rl = 600 ohm Depopulate Rm Rs = 0 ohm For VCC=3.3V, Rl = 900 ohm For VCC=2.5V, Rl = 600 ohm Figure 8 - AC Coupled LVDS input 6 Microsemi Corporation ZLAN-414 4.0 Application Note Footprint Compatibility of ZL40211 with SY89837U The ZL40211 is a 2:8 LVPECL buffer that has been designed to be footprint compatible with the Micrel SY89837U. The following table shows the similarity of the pin map and also highlights the slight differences. Pin ZL40203 Pin Name SY58021U Pin Name Comment 1 clk0_p IN0 2 vt0 VT0 3 clk0_n /IN0 4 ctrl0 VREF-AC0 See differences 5 ctrl1 VREF-AC1 See differences 6 clk1_p IN1 7 vt1 VT1 8 clk1_n /IN1 9 vdd VCC 10 NC CAP 11 out7_n /Q7 12 out7_p Q7 13 out6_n /Q6 14 out6_p Q6 15 out5_n /Q5 16 out5_p Q5 17 out4_n /Q4 18 out4_p Q4 19 vdd VCC 20 gnd gnd 21 gnd gnd 22 vdd VCC 23 out3_n /Q3 24 out3_p Q3 25 out2_n /Q2 26 out2_p Q2 27 out1_n /Q1 28 out1_p Q1 29 out0_n /Q0 30 out0_p Q0 31 sel SEL 32 vdd VCC See differences Table 4 - Pin Commonality between ZL40211 and SY89837U 7 Microsemi Corporation ZLAN-414 Application Note The difference in VREF-AC on the SY89837U and "ctrl" ZL40211 are the same as highlighted for the 1:4 devices. That is, VREF-AC provides a reference voltage that can be used in conjunction with the VT pin to set the bias point for the device. Ctrl is different in that it is a control pin that when asserted engages an internal biasing network. In addition to this difference, the SY89837U requires a capacitor to connected to pin 10 to correctly initialize the Runt Pulse Elimination (RPE) circuit. The pin can be connected directly to Vcc to disable the RPE circuit. This pin is a No-connect on the ZL40211. Refer to Figures 1 to 4 to for guidelines on how to connect vt and ctrl vs VT and VREF-AC on these devices. The treatment of these pins is identical on the 1:4 devices and the 1:8 devices. 8 Microsemi Corporation For more information about all Microsemi products visit our Web Site at www.microsemi.com Information relating to products and services furnished herein by Microsemi Corporation or its subsidiaries (collectively “Microsemi”) is believed to be reliable. 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