Electronic Components Datasheet Search |
|
A3908 Datasheet(PDF) 5 Page - Allegro MicroSystems |
|
A3908 Datasheet(HTML) 5 Page - Allegro MicroSystems |
5 / 8 page 5 Low Voltage DC Motor Driver A3908 5 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com Functional Description Voltage Regulation The A3908 regulates the voltage across the motor coil. The voltage across the OUTA and OUTB terminal is sensed and compared to an internal threshold voltage. The high-side switch will be driven in linear mode to keep the applied voltage maintained at the calculated level, as follows: VOUT = 4 × VREF (R2 / [R1+R2]) , where VREF (VBG) is 1.285 V typical. Then, for forward mode: VOUT = VOUTA – VOUTB , and for reverse mode: VOUT = VOUTB – VOUTA . The alternative method is to provide a tightly regu- lated voltage to the motor supply pin and run the source and sink drivers as switches. The voltage drop across these switches will vary linearly with tempera- ture and current, therefore the voltage across the motor coil also will vary. The A3908 will eliminate these sources of error for a system where controlling the motor voltage is the optimum means of control. Thermal Shutdown The A3908 will disable the out- puts if the junction temperature, TJ , reaches 165°C. There is 15°C of hysteresis, so when the junction temperature drops below 150°C, the device will begin to operate normally. Dropout Mode The source and sink drivers have a total RDS(on) of approximately 1.2 Ω total. When the motor supply voltage, VDD, drops too low compared to the regulated value, the IC enters dropout mode. In this case, the voltage across the motor coil will be: VMOTOR = VDD – ILOAD (RDS(sink) + RDS(src)) Brake Mode When both inputs are high, the A3908 goes into high-side brake mode (turns on both source drivers). There is no protection during braking, so care must be taken to ensure that the peak current does not exceed the absolute maximum current, IOUT. Standby Mode To minimize battery drain, standby mode will turn off all of the circuitry and draw typi- cally less than 100 nA from the VDD line. There will be a very short delay, approximately 2 μs, before enabling the output drivers after release of standby mode. Power Dissipation . Power can be approximated based on the below three components: PD(src) = ILOAD (VDD –VREG) , PD(sink) = ILOAD × RDS(sink) , and Pbias = VDD × IDD. Control Logic Table Settings Resulting Mode IN1 IN2 OUTA OUTB 0 0 Off Off Standby 0 1 Low VREG Reverse 10 VREG Low Forward 1 1 High High Brake |
Similar Part No. - A3908 |
|
Similar Description - A3908 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List 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 |