Epson 890N Service Manual - Page 48

EPSON FX-890/2190 Table 2-2. Major Elements on MAIN Board (continued) Elements Location Function TYPE-B IF circuit † Specification: Level 2 Current consumption 0.5 A max. SSI is supported. Transmission rates supported are 600/1200/2400/4800/ 9600/19200 [bps]. † Data reception rate (between TYPE B and Main Circuit Board) is 2 MB/s at peak. † Data receiving system: DMA † Data reception timing: Based on TYPE-B specification † Power ON reset • Device: Reset IC LA5623M (Sanyo) equivalent reset circuit 2 • Detecting voltage: 4.2 ± 0.2 V (logic system) RESET IC IC13 • Processing: Generates a hardware reset, and there is delay of 60 ms (min.) at turning High from Low. † Power OFF detection • Device: Reset IC LA5623M (Sanyo) equivalent reset circuit 1 • Detecting voltage:1.25 ± 0.05 V (keeps watch on power system by resistor division) • Processing: Divides 42 V source voltage by resistance at 1.4/30, and keeps watch on. Generates NMI interrupt request when 42V source voltage is 28.0 V (min. 26.4 V). Oscillating circuit † Element: Ceramic oscillator † Frequency: 48.00 MHz † Oscillation stabilization time: 10 ms or less Revision B Table 2-2. Major Elements on MAIN Board (continued) Elements Location Function CR Motor Driver IC15 † Drive voltage: 42 V ± 5% † Drive IC: SLA7024M (Sanken) † Drive system: Constant-current unipolar drive † Excitation method: 2-2 phase /1-2 phase (quadrangular) /1-2 phase (circular) /W1-2 phase driving † Current detection resistance:0.68 Ω, 2 W † Current value setting:Setting with D/A port of the CPU D/A reference voltage (= 3.3 ± 0.3 V) The maximum of 8-bit current setting register for D/A (= d'255) Current setting resolution:3.3/255/ 0.68=0.019A † QPIT compensation: D/A circuit is compensated to ensure current accuracy (± 5% at the maximum current and ± 10% at the minimum current). PF Motor Driver † Drive voltage: 42 V± 5% † Drive system: Constant-current bipolar drive † Drive IC: A3972 (Sanken) † Excitation method:1-2 phase † Phase change: The ASIC generates the control signal of IC9 the drive IC based on the trigger signal (CPU output). † Current value setting: Setting with D/A converter of drive IC. Any setting number is available. † Current detection resistance:0.56Ω ± 1%, 1 W † Output at reset: SLEEP signal (G/A output) Low. (Output current off) Head Driver QM1, QM2, QM3 † Drive voltage: 42 V ± 5% † Drive system: Constant voltage drive † Drive Tr: SMA4037 (Sanken) 3A † Control method: Controlled by ASIC based on print timing signal (CPU output) † At reset: G/A output L (head drive off) † QPIT compensation: The voltage detecting circuit is compensated to ensure the accuracy of head energization time. Operating Principles Overview 48