User manual JRC NJU39612E2

[. . . ] For example, NJU39612 has 27, or 128, output levels and therefor has 7 bits resolution. Remember that this is not equal to the number of microsteps available. Linearity Error Linearity error is the maximum deviation from a straight line passing through the end points of the DAC transfer characteristic. [. . . ] Power-on Reset This function automatically resets all internal flip flops at power-on. This results in VSS voltage at both DAC outputs and all digital outputs. Reset can be used to measure leakage currents from VDD. I2 [mA] T max T2 [mNm] Tnom Tmin I I1 [mA] T1 [mNm] Figure 6a. An example of accessible positions with a given torque deviation/fullstep. TNom = code 127. CS 0 0 1 A0 0 1 X Data Transfer D7 --> Sign1, (D6--D0) --> (Q61--Q01) D7 --> Sign2, (D6--D0) --> (Q62--Q02) No Transfer Figure 7. Table showing how data is transfered inside NJU39612. NJU39612 s ABSOLUTE MAXIMUM RATINGS Parameter Pin no. Symbol Min Max Unit Voltage Supply Logic inputs Reference input Current Logic inputs Temperature Storage temperature Operating ambient temperature 4 5-14, 16 1 5-14, 16 VDD VI VRef II Tstg Topr -0. 3 -0. 3 -0. 4 6 VDD+ 0. 3 VDD+ 0. 3 +0. 4 V V V mA °C °C -55 -20 +150 +85 s RECOMMENDED OPERATING CONDITIONS Parameter Symbol Min Typ Max Unit Supply voltage Reference voltage Rise and fall time of WR VDD VRef tr, tf 4. 75 0 - 5. 0 2. 5 - 5. 25 3. 8 1 V V µs NJU39612 s ELECTRICAL CHARACTERISTICS Electrical characteristics over recommended operating conditions. Parameter Symbol Conditions Min Typ Max Unit Logic Input Reset logic HIGH input voltage Reset logic LOW input voltage Logic HIGH input voltage Logic LOW input voltage Reset input current Input current, other inputs Input capacitance Internal Timing Characteristics Address setup time Data setup time Chip select setup time Address hold time Data hold time Chip select hold time Write cycle length Reset cycle length Reference Input Input resistance Logic Outputs Logic HIGH output current Logic LOW output current Write propagation delay Reset propagation delay DAC Outputs Nominal output voltage Resolution Offset error Gain error Endpoint nonlinearity Differential nonlinearity Load error Power supply sensitivity Conversion speed VIHR VILR VIH VIL IIR II VSS < VIR < VDD VSS < VI < VDD 3. 5 2. 0 -0. 01 -1 60 60 70 50 80 6 3 9 -13 5 30 60 0. 1 0. 8 1 1 0 0 0 -5 100 150 V V V V mA µA pF ns ns ns ns ns ns ns ns kohm mA mA ns ns tas tds tcs tah tdh tch tWR tres Rref IOH IOL tpwr tpres Valid for A0 Valid for D0 - D7 VO = 2. 4 V VO = 0. 4 V From positive edge of WR. Outputs valid, Cload = 120 pF From positive edge of Reset to outputs valid, Cload = 120 pF Reset open, VRef = 2. 5 V 2 - VDA 0 - 7 0. 2 0. 1 0. 2 0. 2 0. 1 0. 1 3 tDAC (VDA, unloaded - VDA, loaded) Rload = 2. 5 kohm, Code 127 to DAC Code 127 to DAC 4. 75 V < VDD < 5. 25 V For a full-scale transition to ±0. 5 LSB of final value, Rload = 2. 5 kohm, Cload = 50 pF. VRef - 1LSB 0. 5 0. 5 0. 5 0. 5 0. 5 0. 3 8 V Bits LSB LSB LSB LSB LSB LSB µs NJU39612 t cs CS t as A0 t ds D0-D7 t WR t DAC WR t ch t ah t dh DA t pwr Sign Figure 8. Timing of Reset NJU39612 s APPLICATIONS INFORMATION How Many Microsteps?The number of true microsteps that can be obtained depends upon many different variables, such as the number of data bits in the Digital-to-Analog converter, errors in the converter, acceptable torque ripple, single- or double-pulse programming, the motor's electrical, mechanical and magnetic characteristics, etc. Many limits can be found in the motor's ability to perform properly; overcome friction, repeatability, torque linearity, etc. It is important to realize that the number of current levels, 128 (27), is not the number of steps available. 128 is the number of current levels (reference voltage levels) available from each driver stage. Combining a current level in one winding with any of 128 other current levels in the other winding will make up 128 current levels. [. . . ] Ramping Every drive system has inertia which must be considered in the drive system. Unlike the DC motor, the stepper motor is a synchronous motor and does not change its speed due to load variations. Examining a typical stepper motor's torque-versus-speed curve indicates a sharp torque drop-off for the "start-stop without error" curve. [. . . ]