Electronic Components Datasheet Search |
|
S-8533A27AFT-TB-x Datasheet(PDF) 10 Page - Seiko Instruments Inc |
|
S-8533A27AFT-TB-x Datasheet(HTML) 10 Page - Seiko Instruments Inc |
10 / 33 page STEP-DOWN, SYNCHRONOUS PWM CONTROL SWITCHING REGULATOR CONTROLLER S-8533 Series Rev.3.0_01 10 3. ON/OFF Pin (Shutdown Pin) This pin is used to activate and deactivate the step-down operation. When the ON/OFF pin is set to “L”, all the internal circuits stop working, and substantial savings in current consumption are thus achieved. The voltage of the PDRV pin goes to VIN level and voltage of the NDRV pin goes to VSS level to shut off the respective transistors. The ON/OFF pin is configured as shown in Figure 8. Since pull-up or pull-down is not performed internally, operation where the ON/OFF pin is in a floating state should be avoided. Application of a voltage of 0.3 to 1.8 V to the pin should also be avoided lest the current consumption increases. When the ON/OFF pin is not used, it should be connected to the VIN pin. ON/OFF VIN VSS Figure 8 ON/OFF Pin Structure ON/OFF Pin CR Oscillation Circuit Output Voltage “H” Active Set value “L” Non-active Open 4. 100% Duty Cycle The S-8533 Series operates with a maximum duty cycle of 100%. The switching transistor can be kept on to supply current to the load continually, even in cases where the input voltage falls below the preset output voltage value. The output voltage under these circumstances is equal to the subtraction of the lowering due to the DC resistance of the coil and the on-resistance of the switching transistor from the input voltage. 5. Back-Flow Current Since the S-8533 Series performs PWM synchronous rectification under a light load, current flows backward in the VIN direction. The back-flow current therefore reaches its peak when there is no load (see Figure 9). Pay attention to the maximum back-flow current value, which can be calculated from the following expressions. Duty (IOUT = 0) = VOUT/VIN Example : VIN = 5 V, VOUT = 3 V, Duty = 60% ΔIL = ΔV/L × ton = (VIN − VOUT) × Duty/(L × fOSC) × 1.2 Example : VIN = 5 V, VOUT = 3 V, fOSC = 300 kHz, L = 22 μH, ΔIL = 218 mA ILmax. = ΔIL/2 = 109 mA, ILmin. = −ΔIL/2 = −109 mA When there is no load, the current waveform becomes a triangular wave with the maximum, ILmax., and the minimum, ILmin., which is negative. The negative current, shaded regions in Figure 10, flows backward. When the output current (IOUT) is approximately 109 mA under the above conditions, the current does not flow backward since the minimum value (ILmin) of the triangular wave becomes 0 mA. When an input capacitor (CIN) is installed, back-flow current to the power source is negligible since the back-flow current is absorbed by the input capacitor. The input capacitor is indispensable to reduce back-flow current to the power source. |
Similar Part No. - S-8533A27AFT-TB-x |
|
Similar Description - S-8533A27AFT-TB-x |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | 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 |