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CY7C1512KV18-333BZC Datasheet(PDF) 10 Page - Cypress Semiconductor |
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CY7C1512KV18-333BZC Datasheet(HTML) 10 Page - Cypress Semiconductor |
10 / 33 page CY7C1510KV18, CY7C1525KV18 CY7C1512KV18, CY7C1514KV18 Document Number: 001-00436 Rev. *M Page 10 of 33 Programmable Impedance An external resistor, RQ, must be connected between the ZQ pin on the SRAM and VSS to enable the SRAM to adjust its output driver impedance. The value of RQ must be 5X the value of the intended line impedance driven by the SRAM. The allowable range of RQ to guarantee impedance matching with a tolerance of ±15% is between 175 Ω and 350Ω, with VDDQ =1.5 V. The output impedance is adjusted every 1024 cycles upon power up to account for drifts in supply voltage and temperature. Echo Clocks Echo clocks are provided on the QDR II to simplify data capture on high speed systems. Two echo clocks are generated by the QDR II. CQ is referenced with respect to C and CQ is referenced with respect to C. These are free running clocks and are synchro- nized to the output clock of the QDR II. In the single clock mode, CQ is generated with respect to K and CQ is generated with respect to K. The timing for the echo clocks is shown in Switching Characteristics on page 25. PLL These chips use a PLL that is designed to function between 120 MHz and the specified maximum clock frequency. During power up, when the DOFF is tied HIGH, the PLL is locked after 20 μs of stable clock. The PLL can also be reset by slowing or stopping the input clocks K and K for a minimum of 30 ns. However, it is not necessary to reset the PLL to lock to the desired frequency. The PLL automatically locks 20 μs after a stable clock is presented. The PLL may be disabled by applying ground to the DOFF pin. When the PLL is turned off, the device Application Example Figure 1 shows two QDR II used in an application. Figure 1. Application Example R = 250 ohms Vt R R = 250 ohms Vt Vt R Vt = Vddq/2 R = 50 ohms R CC# D A SRAM #2 R P S # W P S # B W S # ZQ CQ/CQ# Q K# CC# D A K SRAM #1 R P S # W P S # B W S # ZQ CQ/CQ# Q K# BUS MASTER (CPU or ASIC) DATA IN DATA OUT Address RPS# WPS# BWS# Source K Source K# Delayed K Delayed K# CLKIN/CLKIN# K [+] Feedback |
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