Electronic Components Datasheet Search |
|
SC1766CS08 Datasheet(PDF) 7 Page - Semtech Corporation |
|
SC1766CS08 Datasheet(HTML) 7 Page - Semtech Corporation |
7 / 11 page © 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 BATTERY CHARGE CONTROLLER SC1766 Janaury 30, 1998 PRINCIPLES OF OPERATION Battery Properties The basic principle of rechargeable battery systems, including NiMH and NiCd cells, is that the processes of charge and discharge are reversible. The charge char- acteristics of NiMH and NiCd cells look similar in that 1) the cell voltage at the end of charge drops and 2) the cell temperature increases rapidly near the end of charge. The figure below shows the charge voltage and charge temperature characteristics of NiMH and NiCd cells. Notice that the cell voltage decline of NiMH cells at the end of charge is less pronounced than for NiCd cells. Fast battery chargers are available where recharging takes only 1 hour or less with a simple control circuit. One main purpose of the control circuit is to terminate the fast charge process to prevent the temperature and internal pressure of the battery cell from building to a damaging level which degrades or even destroys the battery cell. The SC1766 is a battery fast charge controller IC that utilizes the following methods to terminate the fast charge process for NiMH or NiCd battery cells: 1 Negative delta voltage cut-off (- ∆V ), 2 Peak voltage timer cut-off (0 ∆V ), 3 Maximum temperature cut-off (TCO), 4 Maximum voltage cut-off (VCO), 5 Safety timer cut-off. The principle of operation of the SC1766 is described in the following section. SC1766 Operation When power is first applied to the charge system, con- sisting of rechargeable battery cells, charge current source, the SC1766 and its associated external circuit, all internal digital circuit blocks of the SC1766 are reset by internal power-on-reset circuitry. The internal control unit then checks the battery condition to prevent fast charge from taking place under battery fault conditions, i.e. cell voltage fault (VBT< 0.65V or VBT> 3.7V) or cell temperature fault ( αNTC > αNTCL or αNTC < αNTCH for the 14-pin version). Temperature fault limits corre- sponding to αNTCL and αNTCH are determined by an external thermistor divider circuit as included in the typ- ical application circuit. After the battery passes condi- tion fault checks, the V OUT pin goes to low to start fast charge while the initial timer and safety timer of the SC1766 start counting. Both the negative delta voltage detector and the peak voltage timer, however, are dis- abled until the initial stage of a charge cycle elapses. The SC1766 constantly monitors the voltage at the VBT pin, which rises as battery cells are being fast- charged until the battery full condition is nearly ap- proached. The battery temperature is also constantly sensed to guard against abnormal temperature situa- tions. The V OUT pin will be pulled high by an external pull-up device and the fast charge process will be switched to trickle charge when one of the following situations is encountered: • A negative delta voltage of 0.25% at the VBT pin is detected compared to its peak value ( −∆V), • The battery voltage stays at its peak value for the duration determined by the peak voltage timer set- ting (0 ∆V), • The VBT pin voltage exceeds the “high” battery voltage protection limit (VCO), • The battery temperature, sensed by the thermistor divider, exceeds the fault temperature range (TCO), • The selected safety timer period has finished. TIMER PIN The timer pin can be used as follows to select one of the preset safety timer periods and its corresponding periods of initial timer and peak voltage timer: TIMER pin Safety timer Peak V timer Initial timer VDD 40 min. 2 min. 1.5 min. GND 80 min. 4 min. 3 min. Floating 160 min. 8 min. 3 min. |
Similar Part No. - SC1766CS08 |
|
Similar Description - SC1766CS08 |
|
|
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 |