Motore di ricerca datesheet componenti elettronici |
|
ML4435CP Scheda tecnica(PDF) 8 Page - Micro Linear Corporation |
|
ML4435CP Scheda tecnica(HTML) 8 Page - Micro Linear Corporation |
8 / 14 page PRELIMINARY DATASHEET May, 2000 8 PRELIMINARY ML4435 times the commutation frequency. The TACH out also indicates a low motor speed by staying TTL high when the motor is at its minimum speed (SPEED FB below 0.97V). BACK EMF SAMPLER The input to the VCO (pin 18) SPEED FB is controlled by the Back EMF Sampler. The back EMF sense pins FB A, FB B, and FB C inputs to the back EMF sampler require a signal from the motor phase leads that is below the VCC of the ML4435. The phase sense input impedance is 8.7k Ω. If the motor voltage is greater than the VCC of the ML4435 then this requires a series resistor RFB from the motor phase lead shown in Figure 8. RFB can be selected by using the graph in Figure 9 or using the following equation: VNEUTRAL = (FB A + FB B + FB C)/3 This allows the ML4435 to compare the back EMF signal to the motors neutral point without the need for bringing out an extra wire on a WYE wound motor. For DELTA wound motors there isn’t a physical neutral to bring out so this reference point must be calculated anyway. The back EMF sampler takes the motor phase that is not driven (i.e. if LA and HB are on then phase A is driven low and phase B is driven high then phase C is sampled). The sampled phase provides a back EMF signal that is compared against the neutral of the motor. The sampler is controlled by the commutation state machine. The sampled back EMF is compared to the neutral through an error amplifier. The output of the error amplifier outputs a charging or discharging current to SPEED FB (pin 18) which provides the voltage to the VCO. BACK EMF SENSING PHASE LOCKED LOOP COMMUTATION CONTROL The three blocks: The commutation state machine, the VCO, and the back EMF sampler form a phase locked loop that locks the commutation clock onto the back EMF signal. The complete phase locked loop is illustrated in Figure 10. The phased locked loop requires a lead lag filter that is set by external components on SPEED FB (pin 18). The filter components in Figure 10 work for most applications. If performance is unstable C1 and C2 can go up or down a decade in value as low as the C2 stays equal to C1 x 10. Figure 10. Phase Locked Loop FBA VCO BACK EMF SAMPLER COMMUTATION STATE MACHINE 4 SPEED FB RSFB CSFB2 CSFB 6 5 FBB FBC RSFB2 Figure 9. RFB vs. VMOTOR [MAX] FUNCTIONAL DESCRIPTION RFB = 8.7k ( VMOTOR 12 -1) W The back EMF sampler takes the motor phase voltages divided down to signals that are less than VCC (12V nominal) and calculates the neutral point of the motor by the following equation: Motor Volta e [Max] V 05 20 25 30 2,000 0 4,000 6,000 ,000 0,000 2,000 Figure 8. Back EMF Sampler Configuration BLDC MOTOR RFBA RFBB RFBC FBA ABC 4 FBB 5 FBC 6 |
Codice articolo simile - ML4435CP |
|
Descrizione simile - ML4435CP |
|
|
Link URL |
Privacy Policy |
ALLDATASHEETIT.COM |
Lei ha avuto il aiuto da alldatasheet? [ DONATE ] |
Di alldatasheet | Richest di pubblicita | contatti | Privacy Policy | scambio Link | Ricerca produttore All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |