DS2710G+ Maxim Integrated Products, DS2710G+ Datasheet - Page 8

• Manufacturer Part Number: DS2710G+
• Description: IC NIMH CHRGR SGL-CELL 10-TDFN
• Manufacturer: Maxim Integrated Products

Specifications of DS2710G+

• Function: Charge Management
• Battery Type: Nickel Metal Hydride (NiMH)
• Voltage - Supply: 4 V ~ 5.5 V
• Operating Temperature: -20°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 10-TDFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The DS2710 regulates charge current by maintaining a
constant average voltage across an external sense
resistor connected between the VN1 and VN0 pins.
VN1 and VN0 drive an internal comparator in the
DS2710 to switch the CS output ON and OFF to drive a
regulating pnp bipolar or a pMOS transistor. Hysteresis
on the comparator input provides noise rejection. The
DS2710 regulates the charge current during FAST-
CHARGE to maintain a voltage drop across the sense
resistor as follows:
Figure 3 shows the sense resistor voltage and CS pin
voltage of the regulating circuit during normal operation.
NiMH cells have a low, but finite, impedance. If load
current is flowing out of the battery, an internal voltage
drop appears at the battery terminals. This can interfere
with the CTEST and -ΔV detection. If the load current is
variable, early termination is more likely than if the load
current is constant. If the load’s ground is connected to
the negative terminal of the cell (VN0), load current
flows through the current-sense resistor, resulting in less
Single-Cell NiMH Charger
Table 1. THM Thresholds
Figure 3. Ideal Comparator Input and Charge Control Output
Waveforms
8
V
V
THM THRESHOLD
_______________________________________________________________________________________
SENSE
SENSE
V
CS
STOP
MAX
MIN
= V
Charge-Current Regulation
IREF
NOT DRAWN TO SCALE
- 0.5 x V
Charging with Load Applied
TIME
RATIO OF V
HYS-COMP
0.73
0.33
0.29
CBIAS
= 0.113V (typ)
V
V
V
V
V
OH1
OL1
IREF
SENSE
IREF
- V
(DC)
HYS-COMP
THERMISTOR
RESISTANCE
27.04
4.925
4.085
(k )
charge current to the battery. The load-current return
path should be to charger ground to reduce the likeli-
hood of false termination or impedance-test errors.
Charging with load applied is not recommended.
Accurate temperature sensing is needed to detect tem-
perature FAULT conditions. Connecting an external
10kΩ NTC thermistor between THM and V
10kΩ bias resistor between V
DS2710 to sense temperature. To accurately monitor
the cell, the thermistor should make physical contact
either to the cell or cell tabs. Table 1 shows several rec-
ommended 10kΩ thermistors.
The voltage thresholds of the THM input (V
V
mistor temperature is between 0°C and +45°C when
using the recommended 10kΩ bias resistor and 10kΩ
thermistor circuit. If precharging is in progress and the
voltage on THM reaches V
stops and a FAULT condition is generated. If the volt-
age on THM reaches V
CHARGE or TOP-OFF, charging stops and the DS2710
enters the MAINTENANCE state. FAST-CHARGE and
Figure 4. Ratio of THM Pin to V
THM-MAX
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0
) are set to allow charging to start if the ther-
MIN, MAX Temperature Compare
Semitec 103AT-2
Temperature Monitoring
10
+45
+50
0
TEMPERATURE (°C)
TEMPERATURE (°C)
DIVIDER OUTPUT
20
DD
THM-STOP
THM-STOP
Pin Over Temperature
DD
30
and THM allows the
197-103LAG-A01,
173-103LAF-301
during FAST-
, precharging
Fenwal
+42
+47
40
+4
SS
THM-MIN
and a
50
,