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PDF DS2711 Data sheet ( Hoja de datos )
| Número de pieza | DS2711 | |
| Descripción | (DS2711 / DS2712) Loose Cell NiMH Chargers | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-5826; Rev 4/11
GENERAL DESCRIPTION
The DS2711 and DS2712 are ideal for in-system or
stand-alone charging of 1 or 2 AA or AAA NiMH
“loose” cells. Temperature, voltage, and charge time
are monitored to provide proper fast-charging control
algorithms for nickel metal hydride (NiMH) batteries.
Battery tests are included to detect defective or
inappropriate cells such as alkaline primary batteries.
The DS2711/DS2712 support series and parallel
topologies, with independent monitoring and control of
each cell. Charging of NiCd chemistry cells is also
supported.
APPLICATIONS
Desktop/Stand-Alone Chargers (AAA/AA)
Digital Still Cameras
Music Players
Games
Toys
FEATURES
Charge 1 or 2 NiMH Cells
Detect and Avoid Charging Alkaline Cells
Precharge Deeply Depleted Cells
Fast Charge NiMH with -∆V Termination
Sensitivity of 2mV (typ)
Monitor Voltage, Temperature, and Time for
Safety and Secondary Termination
Regulate Charge Current:
Linear Control (DS2711)
Switch-Mode Control (DS2712)
Drive pMOS or pnp-Type Pass Element or
Switch, or an Optocoupler
Compatible with Popular Optocouplers and
Integrated Primary-Side PWM Controllers
Small 16-Pin SO or TSSOP Packages
DS2711/DS2712
Loose-Cell NiMH Chargers
PIN CONFIGURATION
CC1
CC2
LED1
VSS
LED2
CSOUT
VN1
VN0
1
2
3
4
5
6
7
8
16 VP2
15 VP1
14 THM2
13 THM1
12 VDD
11 TMR
10 CTST
9 DMSEL
SO (150 mils)
TSSOP (4.4mm)
PIN DESCRIPTION
PIN NAME
FUNCTION
1 CC1 Cell 1 Charge-Control Output
2 CC2 Cell 2 Charge-Control Output
3 LED1 Cell 1 Status
4
VSS
Ground Reference and Chip-
Supply Return
5 LED2 Cell 2 Status, Mode-Select Input
6 CSOUT Current-Sense Output
7 VN1 Current-Sense + Input
8 VN0 Current-Sense - Input
9 DMSEL Display-Mode Select
10 CTST Cell Test Threshold Set
11 TMR Charge Timer Set
12 VDD Chip-Supply Input (4.0V to 5.5V)
13 THM1 Cell 1 Thermistor Input
14 THM2 Cell 2 Thermistor Input
15
VP1
Cell 1 Positive-Terminal Sense
Input
16
VP2
Cell 2 Positive-Terminal Sense
Input
1 of 15
1 page  
Figure 2. State Diagram
DS2711/DS2712: Loose-Cell NiMH Chargers
VDD < VPOR -VHYS
(asynchronously from
anywhere)
POR
Standby power
CCx = Hi-Z
LEDx = Hi-Z
VDD > VPOR (3.7V)
Presence
TEST
CCx = Hi-Z
LEDx = No Battery
VBAT > 1.75V
OR
T < 0C
OR
T > 45C
t < PCTimeout
OR
VBAT < 1V
PreCHG
CCx = Active
12.5% Par., 25% Ser.
LEDx = Charging
VBAT < 1.65V
VBAT > 1.75V
VBAT > 1V
AND
t < PCTimeout
AND
T < 50C
t > PCTimeout
OR T < 0
OR T > 50
OR VBAT > 1.75V
FAULT
Standby power
CCx = Hi-Z
LEDx = Fault
Cell Test
CCx = Hi-Z
LEDx = Charging
FAIL:
VON - VOFF > VCTST
t < Fast Timeout
PASS
Fast
CHG
CCx = Active
48% Par., 97% Ser.
LEDx = Charging
32 clock
interval
VBAT > 1.75V
VBAT > 1.75V
(asynchronously
from anywhere)
t < 1s
delta-V detect
OR
t > Fast Timeout
t < Topoff Timeout
Topoff
CHG
CCx = Active
12.5% Par., 25% Ser.
LEDx = Charging
T > 50
T > 50
OR
t > Topoff Timeout
MAINT
CCx = Active 1/64
LEDx = Maintenance
5 of 15
5 Page 
DS2711/DS2712: Loose-Cell NiMH Chargers
Cell Voltage Monitoring
In the 2-cell series mode, the voltage difference between VP2 and VP1 is used to determine the Vcell2 voltage in
the two-cell series stack. The voltage difference between VP1 and VN1 is used to determine the Vcell1 voltage. In
the 1-cell series mode, the difference between VP1 and VN1 is used as the cell voltage. VP2 can be left
disconnected in the 1-cell series mode. In parallel mode, the difference between VP2 and VN1 is used for the
Vcell2 voltage, and the difference between VP1 and VN1 is used for Vcell1 voltage.
Individual cell voltages are monitored for minimum and maximum values, using the VBAT-MIN, VBAT-MAX1 and VBAT-MAX2
threshold limits. Upon inserting a cell or power-up with cells inserted, cell voltages must be less than the VBAT-MAX1
threshold before charging begins. The VBAT-MIN threshold determines whether a precharge cycle should precede the
fast charge cycle, and when to transition from precharge to fast charge. Once fast charging commences, cell
voltages are compared to the VBAT-MAX2 threshold once per second. The comparison occurs while the charge
control pin (CC1 or CC2) controlling current to the cell is active (low). When the charge control pin is active so
charge is applied to the cell, the cell voltage is referred to as the VON voltage. When the charge-control pin is
inactive, the cell voltage is referred to as the VOFF voltage. If VBAT-MAX2 is exceeded in fast charge, charging is halted
and a fault condition is displayed. While fast charge is in progress, cell voltage measurements are stored and
compared to future measurements for charge termination and cell test purposes.
Two types of tests are performed to detect primary alkaline and lithium cells or defective NiMH or NiCd secondary
cells. Cells are tested individually in the series and parallel configurations, so that a single improper or defective
cell can be detected quickly. In the series configuration, a single defective cell will terminate charge for both cells,
whereas the parallel mode continues charging the good cell and stops charging the defective cell.
VCTST is set by the resistance from the CTST pin to ground. The nominal sensitivity of 100mV is set by connecting
an 80kΩ resistor between CTST and VSS. The detection threshold can be set from 32mV to 400mV. The following
formula approximates the setting for the detection threshold.
VCTST = 8000/R (value in V)
-ΔV and Flat Voltage Termination
During fast charge, -∆V detection is performed by comparing successive voltage measurements for a drop of 2mV
in the cell voltage. A hold-off period for -∆V detection begins at the start of fast charging and prevents false
termination in the first few minutes of the charge cycle. Once the hold-off period expires, cell voltage
measurements are acquired every 32 clock cycles (during the CCx off time). When a newly acquired voltage
measurement is greater than any previous one, the new value is retained as the maximum value. When the cell
voltage no longer increases, the maximum value is retained and compared against subsequent values. If the cell
voltage drops by the -∆V threshold, V-∆V, (2mV typ), fast charging is terminated. If the cell voltage remains flat such
that the maximum value persists for a period of 16 minutes (tFLAT), fast charge terminates and top-off charging
begins.
Top-Off and Maintenance
In top-off mode, the charger scales the cell current to 25% of the fast charge current. The charge timer is reset and
restarted with a timeout period of one-half the fast-charge duration. When the charge timer expires in top-off, the
charger enters maintenance and delivers 1/64 of the charge source current to the cells. Maintenance charge
continuous until power is removed, the cell(s) are removed or the DS2711/DS2712 is cycled into and out of
suspend mode by disconnecting the TMR pin.
Selecting the Charge Mode
The charge mode configuration is selected by testing the LED2 pin during startup. An internal current source tests
the state of the LED2 pin by pulling up and pulling down on the pin to determine if it is high, low, or open. The
recommended pullup or pulldown resistor value (if used) is 100kΩ. In the parallel charging circuit diagrams on page
7, no resistor is shown. The current path through the LED and 270Ω resistor is sufficient to pull the LED2 pin high
at power-up to select the parallel mode. See to the mode test current (IMTST) specification in the DC Electrical
Characteristics table to select other pullup values.
11 of 15
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet DS2711.PDF ] | |
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