參數(shù)資料
型號: DS2714
廠商: Maxim Integrated Products, Inc.
英文描述: Quad Loose Cell NiMH Charger
中文描述: 4節(jié)散裝NiMH電池充電器
文件頁數(shù): 8/12頁
文件大?。?/td> 221K
代理商: DS2714
DS2714: Quad Loose Cell NiMH Charger
8 of 12
DETAILED DESCRIPTION
CHARGE ALGORITHM OVERVIEW
A charge cycle begins in one of three ways: With the application of power to the DS2714 with cell(s) already
inserted, with the detection of cell insertion after power-up, or when exiting suspend mode with cell(s) inserted. The
charge cycle begins with Pre-charge qualification to prevent Fast charging of deeply depleted cells or charging
under extreme temperature conditions. Pre-charging is performed at a reduced rate until the cell being charged
reaches V
BAT-LOW
(1V). The algorithm proceeds to a Fast charge phase which includes cell tests to avoid accidental
charging of alkaline cells or NiMH cells which are worn-out or damaged. Fast charging continues as long as the cell
temperature is less than 50°C (based on Thermistor sensors THM 1, 2), the open circuit cell voltage(s) are
between V
BAT-LOW
(1.0V) and V
BAT-MAX1
(1.65V) and the closed ciruit cell voltage(s) are less than V
BAT-MAX2
(1.75V).
Fast charging terminates by the - V (negative delta voltage) or flat voltage method. The Top-Off charge phase
follows to completely charge the cell. After the Top-off charge timer expires, the Maintenance charge phase
continues indefinitely to keep the cells fully charged. Maximum voltage, temperature and charge time monitoring
during all charge phases act as secondary or safety termination methods to provide additional protection from
overcharge. A cell voltage greater than V
BAT-MAX2
(1.75V) will result in a fault condition, and temperature greater
than 50°C (see Table 1) will result in either Fault or Maintenance depending on which charge state the device was
last in. Each cell is monitored independently, and the charge phase of each cell is independently controlled. If a cell
is removed while being charged, the algorithm for that cell slot is completely reset to its Presence Test state without
affecting the charge control states of the other cells.
CHARGE CONFIGURATION
The DS2714 supports four slot standalone chargers. It alternates charge to the four slots every two seconds, with
one half second available to each cell. Removal or insertion of a cell into the charger does not disturb the charge
timing or charge rates of the other cells. Charge pulses are fed alternately to each cell under the control of the CCx
pins so that the charge regimes occur in parallel. The duty cycle on the CCx pins are completely independent of
one another. Transitions from Pre-charge to Fast charge, Fast charge to Top-off and Top-off to Maintenance occur
independently for each cell. The configuration shown in Figure 3 is for charging four cells with a current limited
source of 2A. The effective average fast charge current for each cell is 2A x 0.25 x 15/16 = 0.469A. The 15/16 term
is due to the fact that every 16
charge time slot is used for negative delta-voltage and impedance testing. No
current is delivered to the cell during that time. Mechanical design of the holders is required to prevent insertion of
more than one cell in each slot. The holder design should also prevent electrical contact with reverse polarity
insertion.
PERFORMANCE REQUIREMENTS OVER TEMPERATURE AND VOLTAGE
85
70
50
0
-20
-40
TEMPERATURE, DEGRES
CENTIGRADE
V
4.0
5.5
Full Performance
Valid NiMH
Charge Range
Low
Temperature
Range
High
Temperature
Range
Below Operating
Voltage Range
Abs. Max
Operating
Range
INTERNAL OSCILLATORS AND CLOCK GENERATION
An internal oscillator provides the main clock source used to generate timing signals for internal chip operation. The
pre-charge timer, hold-off timers, and duty factors for the charging operations are derived from this timebase. There
are two separate timers for the impedance test and Fast Charge/Topoff functions.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
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