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042605
DESCRIPTION
The DS2715 is well suited for cost-sensitive charger
applications where the battery is either internal or in a
unique battery pack. It has been optimized for safe
reliable charging of 1 to10 NiMH cells in series. The
DS2715 has an internal gain block that can be
selected as either a comparator or transconductance
amplifier for charge current regulation. The DS2715 is
configurable as a switched DC charger, a linear
current regulator, or a switchmode current source.
The DS2715 pre-conditions severely depleted cells
are pre-conditioned before entering full charge mode.
The DS2715 terminates full charge using the dT/dt
technique. It requires an external thermistor for dT/dt
detection. Over-temperature, under-temperature, and
over-voltage detection prevents charging under
unsafe environmental conditions. A user selectable
charge timer allows charge rates from 0.15C to 2C.
Fast-charge, top-off and charge done modes are
included for highly reliable, safe charging of NiMH
cells. Discharge mode allows the DS2715 to enter a
low power sleep state while the cell pack is being
discharged.
FEATURES
Charges 1 to 10 NiMH Cells
Fast Charges up to a 2C Rate
Pre-Charge and Top-Off Charge Modes Help Cell
Conditioning
Load Detection Allows the DS2715 to Enter Low
Power Sleep Mode (Less than 10A) while the
Cell Pack is Discharged
dT/dt Charge Termination Eliminates Cell Charge
Stress
Monitors Voltage, Temperature, and Time for
Safety and Secondary Termination
Regulates Current through Either Linear Control
or Switch-Mode Control
LED Outputs Display Charge State
Small 16-Pin SO Package
APPLICATIONS
Portable DVD Players
Portable Television Sets
Handheld Gaming
Test Equipment
Handheld POS Terminals
PIN CONFIGURATION
VP2
16
VP1
15
CC1
1
CC2
2
LED1
3
VSS
4
LED2
5
CSOUT
6
VN1
7
VN0
8
THM2
14
THM1
13
VDD
12
TMR
11
CTST
10
DMSEL
9
Table 1.
ORDERING INFORMATION
+ Denotes lead-free package.
OPERATIONAL DIAGRAM
Vch
Vbatt
THM
+
-
Vdd
Sense
DS2715
CHARGE
SOURCE/LOAD
GROUND
Divide by n
n Cells
PART MARKING
PIN-PACKAGE
DS2715Z+
DS2715+
16 SO
DS2715Z+T&R
DS2715+
16 SO Tape-and-Reel
DS2715
NiMH Battery Pack Charge Controller
www.maxim-ic.com
See Table 1 for Ordering Information.
16 SO
C
BIAS
V
CH
V
SS
LED1
LED2
V
SS
CTG
CTG
V
BATT
THM
R
T
V
DD
SNS-
SNS+
DIV
MODE
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, click here:
www.maxim-ic.com/errata
.
DS2715: NiMH Cell Pack Charge Controller
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ABSOLUTE MAXIMUM RATINGS*
Voltage on V
DD
and V
CH
Pins with Respect to V
SS
-0.3V to +18V
Voltage on LED1 and LED2 Pins
-0.3V to +18V
Voltage on SNS-
-0.3V to +0.3V
Voltage on C
BIAS
-0.3V
to
6V
Voltage on all Other Pins
-0.3V to V
Cbias
Continuous Sink Current V
CH
, LED1, and LED2
28mA
Operating Temperature Range
-20C to +85C
Storage Temperature Range
-55C to +125C
Soldering
Temperature
See
IPC/JEDECJ-STD-020
*This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation
sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
(4.5V
V
DD
16.5V; T
A
= 0
C to +70C.)
PARAMETER SYMBOL CONDITIONS MIN
TYP
MAX
UNITS
Supply Voltage
V
DD
(Note
1)
4.5 16.5 V
LED1, LED2 Voltage
V
LED
(Note
1)
0.0
16.5
V
Mode Voltage
V
MODE
(Note
1)
0.0
V
Cbias
V
V
CH
Voltage
V
VCH
(Note
1)
0.0
16.5
V
C
BIAS
Capacitor Range
C
Cbias
.02
.15
F
R
T
Resistor Range
R
Rt
20
240 K
DC ELECTRICAL CHARACTERISTICS
(4.5V
V
DD
16.5V, T
A
= 0
C to +70C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN
TYP
MAX
UNITS
Linear Mode, V
DD
= 16.5V
1.3
1.6
mA
Operating Current
(Note 2)
I
DDA
Comparator Mode,
V
DD
= 16.5V
150 250 A
Idle Current
I
DDS
V
DD
< V
UVLO
10
A
Discharge Current
I
DDD
Discharge latch set (Note 2)
200
A
UVLO Threshold
V
UVLO
V
DD
Rising (Note 3)
3.8
3.9
4.0
V
UVLO Hysteresis
V
UVLO-HYS
V
DD
Falling
35
mV
V
CH
Sink Current
I
OL-Vch
V
OL
= 1.5V
20
mA
LED1, LED2 Sink Current
I
OL-LED
V
OL
= 1.0V
20
mA
Leakage Current, V
CH
,
LED1, LED2
I
LKG
Pin inactive or Device Idle
-1
+1
A
THM Pin Leakage
Current
I
LKG-THM
-1
+1
A
V
BATT
Pin Leakage
Current
I
LKG-Vbatt
-50
+50
nA
C
BIAS
Voltage
V
Cbias
0 < I
Cbias
< 0.4ma
3.9
4.0
4.3
V
DIV Pin Load Current
I
Div
500 uA
Current Sense Amplifier
Gain
G
ERR
100A < I
Vch
< 20mA
5
6.25
7.5
-1
Current Sense
Comparator Gain
G
COMP
(Note
7)
10
-1
DS2715: NiMH Cell Pack Charge Controller
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AC ELECTRICAL CHARACTERISTICS
(4.5V
V
DD
16.5V, T
A
= 0
C to +70C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN
TYP
MAX
UNITS
UVLO Debounce Time
t
UVLO
10
s
Current Sense
Comparator Propagation
Delay
t
COMP
(Note
7)
250 ns
Discharge Detect
Propagation Delay
t
DD
From detection of current
reversal
1
s
Return To Normal
Function (Op-Amp or
Comparator Mode)
t
RNF
Time from reset of
discharge latch
1
s
R
T
Timing Accuracy
t
Rt
(Note
4)
-10 +10 %
Internal Clock Accuracy
t
BASE
-10
+10 %
ELECTRICAL CHARACTERISTICS: CHARGING
(4.5V
V
DD
16.5V, T
A
= 0
C to +70C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN
TYP
MAX
UNITS
Fast Charge Comparator
Threshold
V
FC
Fast
charge
-127 -121 -115 mV
Fast Charge Comparator
Hysteresis
V
HYS-FC
Fast
charge
-31 -28 -25 mV
Top-off and Pre-Charge
Comparator Threshold
V
TO
Top-off and pre-charge
-38
-33
-28
mV
Top-off and Pre-Charge
Comparator Hysteresis
V
HYS-TO
Top-off and pre-charge
-10
-8
-6
mV
Discharge Latch Reset
Threshold
V
DCHG-RST
-15
-10
-5
mV
Discharge Latch Set
Threshold
V
DCHG-SET
Reverse current through
sense resistor
5 10 15 mV
Low Battery Detect
Threshold
V
LB
From presence detect into
pre-charge
0.95 1.0 1.05 V
Cell Detect Threshold
V
DET
1.50 1.55 1.60 V
No Cell Detect Threshold
V
OPEN
1.60 1.65 1.70 V
Presence Detect
Threshold Hysteresis
V
HYS-PD
90
100 110
mV
2.88 2.92 2.96 V
Minimum Charge Temp
V
THM-MIN
(Note 5, 6)
0 C
1.28 1.32 1.36 V
Maximum Charge Temp
V
THM-MAX
(Note 5, 6)
45 C
1.12 1.16 1.20 V
Over Temp
V
THM-STOP
(Note 5, 6)
50 C
dT/dt Detect
T
TERM
0.425 0.5 0.575 C/min
dT/dt Blanking Time
t
BLANK
3.85 4.3 4.75 Min
Fast Charge Timer
Range
t
FC
0.5
6 Hours
Top-Off to Fast Charge
Duration Ratio
1:2
DS2715: NiMH Cell Pack Charge Controller
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Note 1:
Voltages relative to V
SS
.
Note 2:
Does not include current through V
CH
, R
T
, and DIV pins.
Note 3:
Below this voltage no I/O pins are active.
Note 4:
Does not include tolerance of R
T
resistor.
Note 5:
V
BIAS
and resistor tolerances must be added to determine actual threshold.
Note 6:
Specified temperature thresholds are only valid if recommended thermistor types are used.
Note 7:
Specification is guaranteed by design.
DETAILED PIN DESCRIPTION
PIN
NAME
DESCRIPTION
1 C
BIAS
Bypass for Internal Voltage Regulator
2 V
CH
Cell Stack Charge Control Output
3 V
SS
Ground Reference and Chip Supply Return
4 LED1
Charging
Indicator
Output
5 LED2
Done
Indicator
Output
6 V
SS
Ground Reference and Chip Supply Return
7
CTG
Connect to Ground
8
CTG
Connect to Ground
9 MODE
Mode Select. Connect to V
SS
for linear mode of operation or C
BIAS
for comparator
mode of operation.
10 DIV
Thermistor Divider. Stable output to form a resistor divider for measuring
temperature on THM.
11
SNS+
Positive Current Sense. Connect to the pack side of the sense resistor.
12
SNS-
Negative Current Sense. Connect to the cell stack side of the sense resistor.
13 V
DD
Chip Supply Input: +4.0V to +5.5V range.
14 R
T
Failsafe Timeout. Timeout is selected by an external resistor from R
T
to V
SS
.
15 THM
Thermistor Input. Connect to a thermistor located in the cell pack and a divider
resistor from the Div pin.
16 V
BATT
Battery Voltage Sense Input. Connect to a divider from the positive terminal of the
cell stack to measure the voltage of a single cell.
DS2715: NiMH Cell Pack Charge Controller
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Figure 1. BLOCK DIAGRAM
State Machine
Charge
Timer
Regulator
LED1
VDD
LED2
UVLO
Oscillator
+
-
Pre-Charge
Low Cells
Fast Charge
Exit on Full
Or Timeout
25% Top-Off Charge
(Set by Timer)
SNS+
R
E
F
Vbatt
THM
Rt
Cbias
Mode
Vch
DS2715
Rt start-up test
+
-
Disch. Detect
Ref
HV
HV
HV
Done, Waiting for event
to start charging
Pwr
Pwr
Vsns
Ref
121mV,
33mV,
10mV
AMP
or
Comp
@-0.01V
Rt
A
D
C
RS Latch
Latch is set until
Vsns negative WRT Vss
+
-
R
Th
Disable during
discharge
Div
SNS-
VSS
VSS
V
UVLO
Ref
M
U
X
SNS+
Ref
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