W97AH6KB datasheet(62/127 Pages) WINBOND

62 / 127 page

W97AH6KB / W97AH2KB

Publication Release Date: May 15, 2014

Revision: A01-001

- 62 -

7.4.23 Mode Register Write Reset (MRW Reset)

Any MRW command issued to MRW63 initiates an MRW Reset. The MRW Reset command brings the device to the

Device Auto-Initialization (Resetting) State in the Power-On Initialization sequence (see step 3 in sections 7.2.1

“Power Ramp and Device Initialization”). The MRW Reset command may be issued from the Idle state for

LPDDR2-S4 devices. This command resets all Mode Registers to their default values. No commands other than

NOP may be issued to the LPDDR2 device during the MRW Reset period (tINIT4). After MRW Reset, boot timings

must be observed until the device initialization sequence is complete and the device is in the Idle state. Array data

for LPDDR2-S4 devices are undefined after the MRW Reset command.

For the timing diagram related to MRW Reset, refer to 7.2.3

“Power Ramp and Initialization Sequence” figure.

7.4.24 Mode Register Write ZQ Calibration Command

The MRW command is also used to initiate the ZQ Calibration command. The ZQ Calibration command is used to

calibrate the LPDDR2 ouput drivers (RON) over process, temperature, and voltage. LPDDR2-S4 devices support ZQ

Calibration.

There are four ZQ Calibration commands and related timings times, tZQINIT, tZQRESET, tZQCL, and tZQCS. tZQINIT

corresponds to the initialization calibration, tZQRESET for resetting ZQ setting to default, tZQCL is for long calibration,

and tZQCS is for short calibration. See Mode Register 10 (MR10) for description on the command codes for the

different ZQ Calibration commands.

The Initialization ZQ Calibration (ZQINIT) shall be performed for LPDDR2-S4 devices. This Initialization Calibration

achieves a RON accuracy of ±15%. After initialization, the ZQ Long Calibration may be used to re-calibrate the

system to a RON accuracy of ±15%. A ZQ Short Calibration may be used periodically to compensate for temperature

and voltage drift in the system.

The ZQReset Command resets the RON calibration to a default accuracy of ±30% across process, voltage, and

temperature. This command is used to ensure RON accuracy to ±30% when ZQCS and ZQCL are not used.

One ZQCS command can effectively correct a minimum of 1.5% (ZQCorrection) of RON impedance error within

tZQCS

for all speed bins assuming the maximum sensitivities specified in the ‘Output Driver Voltage and Temperature

Sensitiv

ity’. The appropriate interval between ZQCS commands can be determined from these tables and other

application-specific parameters.

One method for calculating the interval between ZQCS commands, given the temperature (Tdriftrate) and voltage

(Vdriftrate) drift rates that the LPDDR2 is subject to in the application, is illustrated. The interval could be defined by

the following formula:

)

(

)

(

Vdriftrate

VSens

Tdriftrate

TSens

ZQCorrecti

where TSens = max(dRONdT) and VSens = max(dRONdV) define the LPDDR2 temperature and voltage

sensitivities.

For example, if TSens = 0.75% /

C, VSens = 0.20% / mV, Tdriftrate = 1C / sec and Vdriftrate = 15 mV / sec, then

the interval between ZQCS commands is calculated as:

15)

(0.20

(0.75

1.5

= 0.4s

For LPDDR2-S4 devices, a ZQ Calibration command may only be issued when the device is in Idle state with all

banks precharged.

No other activities can be performed on the LPDDR2 data bus during the calibration period (tZQINIT, tZQCL, tZQCS).

The quiet time on the LPDDR2 data bus helps to accurately calibrate RON. There is no required quiet time after the

ZQ Reset command. If multiple devices share a single ZQ Resistor, only one device may be calibrating at any given

time. After calibration is achieved, the LPDDR2 device shall disable the ZQ pin

’s current consumption path to reduce

power.

In systems that share the ZQ resistor between devices, the controller must not allow overlap of tZQINIT, tZQCS, or

tZQCL between the devices. ZQ Reset overlap is allowed. If the ZQ resistor is absent from the system, ZQ shall be

connected to VDDCA. In this case, the LPDDR2 device shall ignore ZQ calibration commands and the device will use

the default calibration settings (See section 8.2.6.5

“RONPU and RONPD Characteristics without ZQ Calibration”

Output Driver DC Electrical Characteristics without ZQ Calibration table).

W97AH6KB датащи(PDF) 62 Page - Winbond

W97AH6KB датащи(HTML) 62 Page - Winbond

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL