TN-41-15: DDR3 VOL/VOH Specifications Introduction Technical Note DDR3 SDRAM VOL and VOH Specifications Introduction This technical note describes the proper interpretation and use of V OL and V OH specifications for DDR3 SDRAM, including: • AC/DC conditions, including single-ended AC/DC output levels • AC timing and slew rate load, including the value of RON and equations for calculating RON(PU) and RON(PD) • Output driver DC linearity, including 34Ω output driver DC electrical characteristics • Defining system V OL and V OH • Calculating system V OL and V OH • VOL and V OH will vary depending on system/application loading. This technical note references JEDEC document JESD79-3F and Micron DDR3 SDRAM data sheet specifications. PDF: 09005aef8547ae28 tn-41-15_ddr3_vol_voh_specs.pdf - Rev. A 07/13 EN 1 Micron Technology, Inc. reserves the right to change products or specifications without notice. © 2013 Micron Technology, Inc. All rights reserved. Products and specifications discussed herein are subject to change by Micron without notice. TN-41-15: DDR3 VOL/VOH Specifications DDR3 SDRAM VOL/VOH Specifications DDR3 SDRAM VOL/VOH Specifications AC and DC Conditions The DDR3 SDRAM data sheet shows two specific use conditions V OL and V OH are defined for: • AC Condition – A special condition to check the driver characteristic slew rate with a specific load. This condition is not a pass/fail condition and must be derated if it is being compared to a non-JEDEC test load condition. The original JEDEC specification used a 40Ω load, but it has been changed to 34Ω. • DC Condition – A measurement only for the current-voltage (I-V) linearity curve. It is not a system-level measurement; it is a reference point only. Table 1: Single-Ended AC/DC Output Levels Symbol Parameter DDR3-800, 1066, 1333, 1600 Unit V Notes VOH(DC) DC output HIGH measurement level (I-V curve linearity) 0.8 × VDDQ VOM(DC) DC output mid-measurement level (I-V curve linearity) 0.5 × VDDQ V VOL(DC) DC output LOW measurement level (I-V curve linearity) 0.2 × VDDQ V VOH(AC) AC output HIGH measurement level (output slew rate) VTT + 0.1 × VDDQ V 1 VOL(AC) AC output LOW measurement level (output slew rate) VTT - 0.1 × VDDQ V 1 Note: 1. The swing of ±0.1 × VDDQ is based on approximately 50% of the static, single-ended output HIGH or LOW swing with a driver impedance of 40Ω, and an effective test load of 25Ω to VTT = VDDQ/2. See figure: Reference Load for AC Timing and Output Slew Rate. Figure 1: Reference Load for AC Timing and Output Slew Rate VDDQ DUT CK, CK# RTT = 25Ω DQ, DM DQS, DQS# Reference point Note: PDF: 09005aef8547ae28 tn-41-15_ddr3_vol_voh_specs.pdf - Rev. A 07/13 EN VTT = VDDQ/2 Reference point 1. This figure represents the effective reference load of 25Ω used in defining the relevant AC timing parameters of the device as well as output slew rate measurements. It is not intended to be a precise representation of any particular system environment or a depiction of the actual load presented by a production tester. System designers should use IBIS or other simulation tools to correlate the timing reference load to a system environment. Manufacturers correlate to their production test conditions, which generally consist of one or more coaxial transmission lines terminated at the tester electronics. 2 Micron Technology, Inc. reserves the right to change products or specifications without notice. © 2013 Micron Technology, Inc. All rights reserved. TN-41-15: DDR3 VOL/VOH Specifications DDR3 SDRAM VOL/VOH Specifications AC Timing and Slew Rate Load All timings and slew rate measurements are referenced to an output driver impedance of 34Ω. Note: Originally, JEDEC specified the default output driver impedance as 40Ω, but it has been changed to 34Ω. Output driver impedance (RON) is defined by the value of the external reference resistor RZQ (RZQ = 240Ω nominal): RON(34) = RZQ/7 = 34.3Ω ±10% nominal. The individual pull-up and pull-down resistors are defined as follows: RON(PU) = (VDDQ - V OUT)/|IOUT|, when RON(PD) is turned off RON(PD) = (VOUT)/|IOUT|, when RON(PU) is turned off Figure 2: Output Driver Voltages and Currents Chip in drive mode Output driver VDDQ IPU To other circuitry such as RCV, . . . RON(PU) DQ IOUT RON(PD) VOUT IPD VSSQ PDF: 09005aef8547ae28 tn-41-15_ddr3_vol_voh_specs.pdf - Rev. A 07/13 EN 3 Micron Technology, Inc. reserves the right to change products or specifications without notice. © 2013 Micron Technology, Inc. All rights reserved. TN-41-15: DDR3 VOL/VOH Specifications DDR3 SDRAM VOL/VOH Specifications Table 2: Output Slew Rate – Single-Ended RON = RZQ/7 DDR3-800 DDR3-1066 DDR3-1333 DDR3-1600 DDR3-1866 DDR3-2133 Parameter Symbol Min Max Min Max Min Max Min Max Min Max Min Max Unit Singleended output slew rate SRQse(1) 2.5 5 2.5 5 2.5 5 2.5 5 2.5 5(2) 2.5 5(2) V/ns 1. SR = Slew rate; Q = Query output; se = Single-ended signals. 2. In two cases, a maximum slew rate of 6 V/ns applies for a single DQ signal within a byte lane. Case 1 – Defined for a single DQ signal within a byte lane that is switching to a certain direction (from HIGH to LOW or LOW to HIGH), while all remaining DQ signals in the same byte lane are static (i.e., they stay HIGH or LOW). Case 2 – Defined for a single DQ signal within a byte lane that is switching to a certain direction (from HIGH to LOW or LOW to HIGH), while all remaining DQ signals in the same byte lane are switching to the opposite direction (i.e., from LOW to HIGH or HIGH to LOW, respectively). For the remaining DQ signal switching to the opposite direction, the regular maximum limit of 5 V/ns applies. Notes: Output Driver DC Linearity Output linearity is not tested under system load conditions. The output driver's current is measured to the reference load in the data sheet. The output current is measured at defined V OL/VOH test points. V OL(DC) and V OH(DC) describe these reference points. Note: VOL(DC) and V OH(DC) are not test conditions. Output current is measured at V OL(DC) and V OH(DC) test points for verification of output drive and linearity. Table 3: 34Ω Output Driver DC Electrical Characteristics RON(NOM) Resistor VOUT Min Nom Max Unit Notes 34Ω RON34(PD) VOL(DC) = 0.2 × VDDQ 0.6 1.0 1.1 RZQ/7 1, 2, 3 VOM(DC) = 0.5 × VDDQ 0.9 1.0 1.1 RZQ/7 1, 2, 3 VOH(DC) = 0.8 × VDDQ 0.9 1.0 1.4 RZQ/7 1, 2, 3 RON34(PU) Pull-up/pull-down mismatch (MMPUPD) Notes: PDF: 09005aef8547ae28 tn-41-15_ddr3_vol_voh_specs.pdf - Rev. A 07/13 EN VOL(DC) = 0.2 × VDDQ 0.9 1.0 1.4 RZQ/7 1, 2, 3 VOM(DC) = 0.5 × VDDQ 0.9 1.0 1.1 RZQ/7 1, 2, 3 VOH(DC) = 0.8 × VDDQ 0.6 1.0 1.1 RZQ/7 1, 2, 3 VOM(DC) = 0.5 × VDDQ –10 N/A 10 % 1, 2, 4 1. Tolerance limits assume RZQ = 240Ω ±1% and are applicable after proper ZQ calibration has been performed at a stable temperature and voltage. Refer to the Output Driver Sensitivity section if either the temperature or the voltage changes after calibration. 2. Tolerance limits are specified under the following conditions: VDDQ = VDD; VSSQ = VSS. 3. Pull-down and pull-up output driver impedance are recommended to be calibrated at 0.5 × VDDQ. Other calibration schemes may be used to achieve the linearity specification above (calibration at 0.2 × VDDQ and 0.8 × VDDQ). 4 Micron Technology, Inc. reserves the right to change products or specifications without notice. © 2013 Micron Technology, Inc. All rights reserved. TN-41-15: DDR3 VOL/VOH Specifications DDR3 SDRAM VOL/VOH Specifications 4. Equation for mismatch between pull-up and pull-down (MMPUPD); measure both RON(PU) and RON(PD) at 0.5 × VDDQ: RON(PU) - RON(PD) MMPUPD = × 100 RON,nom Defining System VOL and VOH The SDRAM is not required to achieve the V OL and V OHvalues stated in the data sheet. Actual system V OL and V OH are determined by the output drive from SDRAM, coupled with the load being driven. System V OL and V OH are usage conditions, not DDR3 SDRAM specifications. Those values are determined by R ONdrive and ODT or the load being driven. Calculating System VOL and VOH System V OL and V OH can be estimated using worst-case values: RON = Largest value; ODT = Smallest value RON(max) = 34.3Ω x 1.11 = 38Ω (properly calibrated; no V/T shift) ODT60(min) = 60Ω x 0.59 = 35Ω (properly calibrated; no V/T shift) If V DDQ = 1.5V and V SS = 0.0V (ideal values): Expected V OL = ~390mV (0.26VDDQ, which is >0.2VDDQ) Expected V OH = ~1.11V (0.74VDDQ, which is <0.8VDDQ) As noted, values are different from the limits stated in the data sheet. Figure 3: VOL Schematics VDDQ 0.5(VDDQ) VDDQ ODT (or equivalent RLOAD) RPU 34W RON PDF: 09005aef8547ae28 tn-41-15_ddr3_vol_voh_specs.pdf - Rev. A 07/13 EN 34W RON RPD VOL = (0.5 × VDDQ) - VSS × 0.5(VDDQ) 34W (34W + ODT) 5 + VSS Micron Technology, Inc. reserves the right to change products or specifications without notice. © 2013 Micron Technology, Inc. All rights reserved. TN-41-15: DDR3 VOL/VOH Specifications Conclusion Figure 4: VOH Schematics VDDQ 34W RON VDDQ VDDQ 34W RON RPU ODT (or equivalent RLOAD) RPD 0.5(VDDQ) VOH = VDDQ - 34W × (VDDQ - (0.5 × VDDQ)) (34W + ODT) Conclusion Data sheet parameters V OL(DC) and V OH(DC) are reference points to which DDR3 SDRAM output driver currents are measured to confirm driver linearity. There is no specified test condition or specification requirement related to those two parameters. System V OL and V OH are system-dependent, and the data sheet parameters V OL(DC) and VOH(DC) cannot be applied to DDR3 SDRAM system performance. A V OL that is too high or a V OH that is too low indicates a violation of the DDR3 SDRAM specification. This can happen if RON impedance is too low or if ODT impedance is too high. PDF: 09005aef8547ae28 tn-41-15_ddr3_vol_voh_specs.pdf - Rev. A 07/13 EN 6 Micron Technology, Inc. reserves the right to change products or specifications without notice. © 2013 Micron Technology, Inc. All rights reserved. TN-41-15: DDR3 VOL/VOH Specifications Revision History Revision History Rev. A – 07/13 • Initial release 8000 S. Federal Way, P.O. Box 6, Boise, ID 83707-0006, Tel: 208-368-3900 www.micron.com/productsupport Customer Comment Line: 800-932-4992 Micron and the Micron logo are trademarks of Micron Technology, Inc. All other trademarks are the property of their respective owners. This data sheet contains minimum and maximum limits specified over the power supply and temperature range set forth herein. Although considered final, these specifications are subject to change, as further product development and data characterization sometimes occur. PDF: 09005aef8547ae28 tn-41-15_ddr3_vol_voh_specs.pdf - Rev. A 07/13 EN 7 Micron Technology, Inc. reserves the right to change products or specifications without notice. © 2013 Micron Technology, Inc. All rights reserved.