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TC649 数据表(PDF) 7 Page - Microchip Technology |
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TC649 数据表(HTML) 7 Page - Microchip Technology |
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7 / 28 page  2002 Microchip Technology Inc. DS21449C-page 7 TC649 4.0 SYSTEM BEHAVIOR The flowcharts describing the TC649’s behavioral algorithm are shown in Figure 4-1. They can be summarized as follows: 4.1 Power-Up (1) Assuming the device is not being held in shutdown or auto-shutdown mode (VIN > VAS)... (2) Turn VOUT output on for 32 cycles of the PWM clock. This ensures that the fan will start from a dead stop. (3) During this Start-up Timer, if a fan pulse is detected, branch to Normal Operation; if none are received… (4) Activate the 32-cycle Start-up Timer one more time and look for fan pulse; if a fan pulse is detected, proceed to Normal Operation; if none are received… (5) Proceed to Fan Fault. (6) End. 4.2 Normal Operation Normal Operation is an endless loop which may only be exited by entering shutdown mode, auto-shutdown mode or Fan Fault. The loop can be thought of as exe- cuting at the frequency of the oscillator and PWM. (1) Reset the missing pulse detector. (2) Is TC649 in shutdown or auto-shutdown mode? If so… a. VOUT duty cycle goes to zero. b. FAULT is disabled. c. Exit the loop and wait for VIN > (VAS + VHAS) to resume operation. (3) Drive VOUT to a duty cycle proportional to VIN on a cycle by cycle basis. (4) If a fan pulse is detected, branch back to the start of the loop (1). (5) If the missing pulse detector times out … (6) Activate the 3-cycle Diagnostic Timer and look for pulses; if a fan pulse is detected, branch back to the start of the loop (1); if none are received… (7) Activate the 32-cycle Start-up Timer and look for pulses; if a fan pulse is detected, branch back to the start of the loop (1); if none are received… (8) Quit Normal Operation and go to Fan Fault. (9) End. 4.3 Fan Fault Fan Fault is an infinite loop wherein the TC649 is latched in shutdown mode. This mode can only be released by a reset (i.e., VIN being brought below VSHDN, then above (VAS + VHAS) or by power-cycling). (1) While in this state, FAULT is latched on (low) and the VOUT output is disabled. (2) A reset sequence applied to the VIN pin will exit the loop to Power-up. (3) End. |
类似零件编号 - TC649 |
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类似说明 - TC649 |
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