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SS6781AG Fiches technique(PDF) 9 Page - Silicon Standard Corp. |
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SS6781AG Fiches technique(HTML) 9 Page - Silicon Standard Corp. |
9 / 18 page www.SiliconStandard.com 9 of 18 SS6781A(G) 1/11/2005 Rev.2.10 APPLICATION INFORMATION OPERATION OF THE SS6781A Power-on and Battery Pre-qualifying When power is first applied to the SS6781A, all internal digital circuit blocks of the SS6781A are reset by the internal power-on-reset circuitry and output LEDs (depending on the setting of SEL1 and SEL2 pins) flash 3 times to indicate the initiation of power-on. The internal control unit then examines the battery condition through the VBT and VTS pins. The acceptable limits of VBT pin are determined by the input voltage of SEL3 pin and the acceptable temperature sense voltage window for VTS pin is 0.29 VCC to 0.72 VCC. If the voltage of VBT pin fails to fall within the predetermined acceptable limits, the SS6781A enters a charge-suspending mode, in which all the internal circuitry remains in reset state. If the voltage of VTS pin is outside the 0.29 VCC to 0.72 VCC window, action of SS6781A is determined by the input voltage of SEL3 pin. Discharge-Before-Charge The SS6781A provides the function of discharge-before-charge to precondition NiCd batteries which suffer from memory effect. This function can only be activated after the pre-qualification of battery voltage and temperature, but before the charge completion is registered for the fast charge cycle. To trigger this function, DSW pin has to be biased to GND for over 0.18 second. After discharge begins, LED1 and LED2 pins are both off, ICON pin is on, and DIS pin goes high to activate an external circuit to discharge the battery until the voltage of VBT pin falls below 0.9V (or 0.69V, depending on the input voltage of SEL3 pin) or DSW pin is biased to GND for over 0.18 second again. Fast charge will automatically start after discharge is finished. The application circuit is included in TYPICAL APPLICATION CIRCUIT. Fast Charge After the battery passes fault checks and required discharging of the battery is completed, fast charging begins while initial timer and safety timer of the SS6781A start counting. Functions of - ∆V detection, peak voltage timer, t T/ ∆ ∆ detection, and maximum battery voltage are, however, disabled temporarily until the initial timer period in the initial stage of a charge cycle elapses. The initial timer period is equal to 1/80 of safety timer. Since the low limit of acceptable VBT voltage is only about 0.16V during the initial timer period, even deeply discharged batteries can easily qualify to be fast charged subsequently. In the course of fast charge, the SS6781A constantly monitors the voltages at VBT and VTS pins. The fast charge process is switched to trickle charge when any one of the following situations is encountered, which are explained below: l Negative delta voltage (- ∆V) l Peak voltage timer (0 V ∆ ) l Delta temperature/ delta time ( ∆T/∆t) l Maximum charge time l Maximum battery voltage l Maximum battery temperature - ∆V Cutoff The SS6781A makes a voltage sampling at VBT pin every 4 seconds when safety timer period is set equal to 80 minutes. If a negative delta voltage of 0.25% compared to its peak value is detected at VBT pin, the fast charge cycle is terminated. 0 ∆V Cutoff If the battery voltage stays at its peak value or decreases very slowly for the duration determined |
Numéro de pièce similaire - SS6781AG |
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Description similaire - SS6781AG |
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