L6258 STMicroelectronics, L6258 Datasheet
L6258
Specifications of L6258
Available stocks
Related parts for L6258
L6258 Summary of contents
Page 1
... TTL/CMOS compatible inputs ■ Cross conduction protection ■ Thermal shutdow Description L6258 is a dual full bridge for motor control applications realized in BCD technology, with the capability of driving both windings of a bipolar stepper motor or bidirectionally control two DC motors. L6258 and a few external components form a complete control and drive circuit ...
Page 2
... Error amplifier and sense amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.5 Effect of the Bemf of the current control loop stability . . . . . . . . . . . . . . . 22 4 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 4.1 Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 4.2 Motor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4.3 Unused inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4.4 Notes on PCB design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5 Operation mode time diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 6 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2/32 L6258 ...
Page 3
... L6258 List of tables Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Table 2. Absolute maximum rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Table 3. Pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Table 4. Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 5. Current levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Table 6. Charge pump capacitor's values Table 7. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 List of tables 3/32 ...
Page 4
... Aloop bode plot (compensated Figure 10. Electrical model of the load Figure 11. Typical application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Figure 12. Full step operation mode timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Figure 13. Half step operation mode timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Figure 14. 4 bit microstep operation mode timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Figure 15. PowerSO36 mechanical data & package dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4/32 L6258 ...
Page 5
... L6258 1 Block diagram Figure 1. Block diagram C VCP2 P VCP1 CHARGE PUMP VREF1 I3_1 I2_1 DAC I1_1 I0_1 PH_1 V (5V) VR GEN DD VREF1 I3_2 I2_2 DAC I1_2 I0_2 PH_2 TRI_CAP TRI_0 TRIANGLE GENERATOR TRI_180 C FREF GND Table 2. Absolute maximum rating Parameter ref1 ref2 boot ...
Page 6
... OUT1A Bridge output connection (1) Disables the bridges for additional safety during switching. DISABLE When not connected the bridges are enabled Triangular wave generation circuit capacitor. The value of TRI_cap this capacitor defines the output switching frequency L6258 36 PWR_GND 35 SENSE1 34 OUT1B 33 I3_1 ...
Page 7
... L6258 Table 3. Pin functions (continued) Pin # 13 18 Note: The number in parenthesis shows the relevant Power Bridge of the circuit. Pins 18, 19, 1 and 36 are connected together. Name V (5V) Supply voltage input for logic circuitry DD GND Power ground connection of the internal charge pump circuit ...
Page 8
... DD j Description Test condition 40V S Off threshold Off threshold Both bridges ON, no load Both bridges OFF operative current T Ambient Thermal J-A resistance (˚C) (˚C/ D02IN1370 80 100 120 140 D02IN1371 Min. Typ 3.3 L6258 160 Max. Unit 1.25 V 7 ...
Page 9
... L6258 Table 4. Electrical characteristics (continued Parameter ΔT Shut down hysteresis SD-H T Thermal shutdown SD Triangular oscillator f osc frequency TRANSISTORS I Leakage current DSS R On resistance ds(on) V Flywheel diode voltage f CONTROL LOGIC V lnput voltage in(H) V Input voltage in(L) I Input current in I Disable pin input current ...
Page 10
... The current control is generated through a switch mode regulation. With this system the direction and the amplitude of the load current are depending on the relation of phase and duty cycle between the two outputs of the current control loop. The L6258 power stage is composed by power DMOS in bridge configuration shown in Figure 4, where the bridge outputs OUT_A and OUT_B are driven the inputs IN_A and IN_B while are driven to ground with a low level at the same inputs ...
Page 11
... L6258 2.1 Reference voltage The voltage applied to VREF pin is the reference for the internal DAC and, together with the sense resistor value, defines the maximum current into the motor winding according to the following relation: where R = sense resistor value s Figure 4. Power bridge configuration ...
Page 12
... The current level in the motor winding is selected according to this table: Table 5. Current levels 12/32 Tri_0 ERROR AMPL Tri_180 VSENSE + Gs=1/Rb SENSE TRANSCONDUCTANCE AMPL POWER AMPL. VS OUTA - + OUTB D97IN625 Current level IMAX H No Current L 9.5 H 19.1 L 28.6 H 38.1 L 47.6 H 55.6 L 63.5 H 71.4 L 77.8 H 82.5 L6258 LOAD ...
Page 13
... L6258 Table 5. Current levels (continued 2.3 Phase input ( PH ) The logic level applied to this input determines the direction of the current flowing in the winding of the motor. High level on the phase input causes the motor current flowing from OUT_A to OUT_B through the load. 2.4 ...
Page 14
... As we have already mentioned, in this situation, the two outputs OUT_A and OUT_B are simultaneously driven from V case is zero and no current flows in the motor winding. 14/32 equal to zero, the transconductance loop is balanced at the value of Vr, to ground; and the differential voltage across the load in this s L6258 Figure 6. ...
Page 15
... L6258 With a positive differential voltage on V positively unbalanced respected Vr. In this case being the error amplifier output voltage greater than Vr, the output of the first comparator is a square wave with a duty cycle higher than 50%, while the output of the second comparator is a square wave with a duty cycle lower than 50%. ...
Page 16
... The block diagram shows the schematics of the L6258 internal current control loop working in PWM mode; the current into the load is a function of the input control voltage V ...
Page 17
... L6258 Gain and bandwidth must be chosen depending on many parameters of the application, like the characteristics of the load, power supply etc..., and most important is the stability of the system that must always be guaranteed. To have a very flexible system and to have the possibility to adapt the system to any application, the error amplifier must be compensated using an RC network connected between the output and the negative input of the same ...
Page 18
... V out ⋅ ---------------------- R V sense = sense ACload = -------------------- - = ---------------------- v R out R S ⋅ ACload dB 20 log ---------------------- = R L 0.33 ⋅ ----------------------- - Aload log 12 + 0.33 , the load has a pole at the frequency Fpole = -------------------------------- - L L ⋅ -------------------- - 2π Fpole = ---------------------------------------- - = 3 – ⋅ ⋅ ----------------------- - 6. 0.33 29.5dB = – 31.4dB S 163Hz L6258 ...
Page 19
... L6258 Before analysing the error amplifier block and the sense transconductance block, we have to do this consideration: Aloop = Ax| = ACpw and Bx| = ACerr this means that Ax|dB is the sum of the power amplifier and load blocks; Ax| = (29,5) + (-31.4) = -1.9dB dB The BODE analysis of the transfer function of Ax is: Figure 7 ...
Page 20
... The transfer function of the Bx block with the compensation on the error amplifier is: 20/32 Verr_out = -(ic · Zc -(Verr_out · 1 ------- - Vsense · = -(Verr_out · Rb Verr_out Bx = – ----------------------- - = – Vsense dB Aloop = AxdB + ------ - ) Zc 1 ------ - ) Zc Zc ------- - Rb and Bx is L6258 ...
Page 21
... L6258 In this case the Bx block has a DC gain equal to the open loop and equal to zero at a frequency given by the following formula: In order to cancel the pole of the load, the zero of the Bx block must be located at the same frequency of 163Hz; so now we have to find a compromise between the resistor and the capacitor of the compensation network ...
Page 22
... In this way the result is a shift of the total Aloop transfer function greater value. 3.5 Effect of the Bemf of the current control loop stability In order to evaluate what is the effect of the Bemf voltage of the stepper motor we have to look at the load block: 22/32 L6258 ...
Page 23
... L6258 Figure 10. Electrical model of the load OUT+ OUT- The schematic now shows the equivalent circuit of the stepper motor including a sine wave voltage generator of the Bemf. The Bemf voltage of the motor is not constant, its value changes depending on the speed of the motor. Increasing the motor speed the Bemf voltage increases: Bemf = Kt · ...
Page 24
... The EA_IN1 and EA_IN2 pins carry out high impedance lines and care must be taken to avoid coupled noise on this signals. The suggestion is to put the components connected to this pins close to the L6258, to surround them with ground tracks and to keep as far as possible fast switching outputs of the device. Remember also an 1 Mohm resistor between EA_INx and EA_OUTx to avoid output current spike during supply startup/shutdown ...
Page 25
... Since the circuit can drive a constant current through the motor, its temperature might exceed, both at low and high speed operation. 4.3 Unused inputs Unused inputs should be connected to the proper voltage levels in order to get the highest noise immunity 13,31 7 L6258 2 SOP36 4 PACKAGE ...
Page 26
... Because the IC uses the board as a heat sink, the dissipating copper area must be sized in accordance with the required value of R 26/32 . thj-amb L6258 ...
Page 27
... L6258 5 Operation mode time diagrams Figure 12. Full step operation mode timing diagram (Phase - DAC input and motor current) Position 0 5V Phase Phase I0_1 0 5V I1_1 0 DAC 1 Inputs 5V I2_1 0 5V I3_1 0 5V I0_2 0 DAC 2 Inputs 5V I1_2 0 5V I2_2 0 I3_2 0 Motor drive Current 1 ...
Page 28
... I0_2 I1_2 DAC 2 Inputs I2_2 I3_2 100% 71.4% Motor drive Current 1 -71.4% -100% 100% 71.4% Motor drive Current 2 -71.4% -100% 28/ Ph2 D97IN627C Half Step Vector Ph1 Ph1 Current level 100 Current L6258 Ph2 0 MAX ...
Page 29
... L6258 Figure 14. 4 bit microstep operation mode timing diagram (Phase - DAC input and motor current) Position Phase Phase 5V 2 I0_1 0 5V I1_1 0 DAC 1 Inputs 5V I2_1 0 5V I3_1 0 5V I0_2 0 DAC 2 Inputs 5V I1_2 0 5V I2_2 0 I3_2 0 Motor drive Current 1 0 Motor drive ...
Page 30
... L6258 OUTLINE AND MECHANICAL DATA PowerSO-36 0096119 C ...
Page 31
... Last Issue in ST-Press DMS 6 First Issue in EDOCS DMS Restyling of the graphic form, changed all V delete TSD parameter in the Electrical characteristic on 7 NOT FOR NEW DESIGN, it has been replaced by equivalent L6258EX. Changed on the page 5 the f 8 18.5kHz Document reformatted. 9 Modified the ACpw formula in ...
Page 32
... Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan - Malaysia - Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America 32/32 Please Read Carefully: © 2007 STMicroelectronics - All rights reserved STMicroelectronics group of companies www.st.com L6258 ...