SI-7600中文资料

98

SI-7600/SI-7600D

s Electrical Characteristics

s Recommended Operating Voltage Ranges

s Absolute Maximum Ratings

99

SI-7600/SI-7600D

s Internal Block Diagram/Diagram of Standard External Circuit

s External Dimensions (Unless specified otherwise, all values are typical)

(Units: mm)

100

SI-7600/SI-7600D

1. Outline

The SI-7600/SI-7600D is a control IC used with a power MOS FET array to drive a 3-phase stepper motor. Select the output-stage MOS FET according to the rated current of the motor.The full step is 2-phase excitation when this IC is in a star con-nection but 3-phase excitation when it is in a delta connection.

2. Features

q Suitable for both star connection drive and delta connection drive q Maximum load supply voltage V BB =45V q Control logic supply voltage Vcc=3 to 5.5V

q Supports star connection (2/2-3phase excitation) and delta connection (3/2-3phase excitation)q Step switching timing by clock signal input q Forward/reverse, hold, and motor-free control

q Step switching at the positive edge or positive/negative edge of the clock signal

q Control current automatic switching function for 2-3phase ex-citation (effective for star connection)

(Current control: 86% for 2-phase excitation, 100% for 3-phase excitation)

q Self-excitation constant-current chopping by external C/R q Slow Decay, Mixed Decay, or Fast Decay selectable q Two package lineup: SOP (surface mounting) and DIP (lead insertion)

SOP …SI-7600, DIP …SI-7600D

q Maximum output current depends on the ratings of the MOS FET array used

Select CW/CCW, Full/Half, or Edge when the clock level is low.Note 1:The control current is always 85% for the full step (2-phase excitation) when the Mode terminal level is high.The value of 100% control current is calculated at the V REF /(5×Rs) terminal because a 1/5 buffer is built into the reference section.

Note 2:When the Edge terminal level is set high, the internal

counter increments both at the rising and falling edges.Therefore, the duty ratio of the input clock should be set at 50%.

Note 3:When the Reset terminal level is set high, the internal counter is reset. Output remains disabled as long as the Reset terminal level is high.

4. Determining the control current

The control current Io can be calculated as follows:When the Mode terminal level is low I O ?V REF /(5×R S )

When the Mode terminal level is high I O ?V REF /(5×R S )→ 3-phase excitation I O ?V REF /(5.88×R S )→ 2-phase excitation

The reference voltage can be set within the range of 0.2V to Vcc ?2V.(When the voltage is less than 0.2V, the accuracy of the refer-ence voltage divider ratio deteriorates.)

5.About the Current Control System (Setting the Constant Ct/Rt)

The SI-7600 uses a current control system of the self-excitation type with a fixed chopping OFF time.

The chopping OFF time is determined by the constant Ct/Rt.The constant Ct/Rt is calculated by the formula T OFF ?1.1×Ct ×Rt (1)

The recommended range of constant Ct/Rt is as follows:Ct: 420 to 1100pF Rt: 15 to 75k ?

(Slow Decay or Mixed Decay →560pF/47k ?, Fast Decay →470pF/20k ?)

Usually, set T OFF to a value where the chopping frequency be-comes about 30 to 40kHz.

The mode can be set to Slow Decay, Fast Decay, or Mixed De-cay depending on the PFD terminal input potential.

the chopping OFF time and by the PFD input voltage V PFD .Formula (1) is used to determine the chopping OFF time.The Fast Decay time is then determined by the RC discharge time from the RC voltage (about 1.5V) to the PFD input voltage (V PFD ) when chopping is turned from ON to OFF .The Fast Decay time is

(2)

The Slow Decay time (t OFFs ) is calculated by subtracting the value of (2) from that of (1).t OFFS ?T OFF ?t OFFf (3)

Application Notes

t OFFf ??R T ×C T ×l n ( )V PFD

1.5

101

SI-7600/SI-7600D

depending on the actual excitation method as follows:a) 2-phase excitation (T=T ON +T OFF )P P = (P1×T ON /T+P2×t OFFf /T)× (1/3)b) 2-3 phase excitation (T=T ON +T OFF )

P P =(P1×T ON /T+P2×t OFFf /T)×(1/4)+(0.5×P1×T ON /T+P2×t OFFf /

T)×(1/12)

When selecting a heatsink for SLA5017, be sure to check the product temperature when in use in an actual applicaiton.The calculated loss is an approximate value and therefore con-tains a degree of error.

Select a heatsink so that the surface Al fin temperature of SLA5017 will not exceed 100°C under the worst conditions.

102

SI-7600/SI-7600D

7. I/O Timing Chart