DS2715Z+ Maxim Integrated Products, DS2715Z+ Datasheet - Page 11

• Manufacturer Part Number: DS2715Z+
• Description: IC NIMH CHARGER 16-SOIC
• Manufacturer: Maxim Integrated Products

Specifications of DS2715Z+

• Function: Charge Management
• Battery Type: Nickel Metal Hydride (NiMH)
• Voltage - Supply: 4.5 V ~ 16 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Operating Supply Voltage: 16.5 V
• Supply Current: 1.3 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 20 C
• Charge Safety Timers: Yes
• Mounting Style: SMD/SMT
• Temperature Monitoring: Yes
• Uvlo Start Threshold: 3.9 V
• Uvlo Stop Threshold: 35 mV
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 3. Ideal Comparator Input and Charge Control Output Waveforms
Charge Rate Selection
The charge rate is determined by an external sense resistor connected between the SNS+ and SNS- pins. The
DS2715 will regulate the charge current to maintain a voltage drop of V
mode) across the sense resistor during FAST-CHARGE. The sense resistor can therefore be selected by:
Timeout Selection
The various charge modes employ different timers to ensure reliable and safe charging. PRECHARGE has a fixed
30 minute limit generated by an internal oscillator. A fault is generated if this time limit is exceeded. FAST-
CHARGE mode normally operates until its dT/dt termination scheme activates. In the event that the dT/dt sensing
does not perform correctly, a safety timeout is required. This timeout is set by an external resistor on the Rt pin to
V
should be chosen so that the timeout is greater than the FAST-CHARGE time expected in the application, but not
so much greater that its protection is compromised. If the timer expires during FAST-CHARGE, the timer count is
reset and charging proceeds to the TOPOFF charge phase. The Rt resistor also sets the timed charge duration of
TOPOFF mode. The TOPOFF time-out period is fixed at half (a quarter for the DS2715B) of the FAST-CHARGE
time-out period. When the timer expires in TOPOFF, the DS2715 enters the DONE state.
Resistors can be selected to support fast-charge time-out periods of 0.5 to 6 hours and TOPOFF charge time-out
periods of 0.25 to 3 hours (0.125 to 1.5 hours for the DS2715B). The programmed FAST-CHARGE time
approximately follows the equation:
SS
and provides secondary protection against significant overcharging. As such, the value of the Rt resistor
Linear Mode:
Comparator Mode:
V
|V
CH
sns
|
t(minutes) = 1.5 x R(ohms) / 1000
R = |V
R = |(V
FC
Not drawn to scale
FC
/ Desired FAST-CHARGE Current|
+ 0.5 x V
Time
11 of 17
HYS-FC
) / Desired FAST-CHARGE Current|
FC
(or V
FC
V
V
|V
|V
|V
Pullup
OL
+ 0.5 x V
FC
sns
FC
|
(DC)|
+ V
HYS-FC
HYS-FC
|
in comparator