DS2715Z+ Maxim Integrated Products, DS2715Z+ Datasheet - Page 9

• 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

Suspension of charge activity is possible by floating the R
presence test conditions when suspending from a charge mode. The DISCHARGE mode is not affected by the
SUSPEND function. The Vch output is high-impedance for charging modes, and operates as normal for
DISCHARGE mode during SUSPEND. The SUSPEND function is useful for resetting the DS2715 in applications
where the batteries are not removed from the circuit and DISCHARGE mode is not utilized. It also allows for a
means to stop charging by the application circuit, such as with a microcontroller signal for example.
DISCHARGE Mode
When the DS2715 detects a discharge current voltage drop of V
charging is terminated and the DS2715 enters the DISCHARGE state. Initially, the discharge current must flow
through the parasitic diode of the PFET regulating transistor until the DS2715 switches to DISCHARGE mode.
While in this mode, voltage sensing, thermal sensing, and the LED1 output are disabled. The V
to fully bias the charge control transistor into a low impedance state and allow the pack to be discharged. Current
drain of the DS2715 drops to I
sense resistor causes a sense voltage of at least V
events occur, the DS2715 enters the PRESENCE state to begin a new charge cycle.
LED1 Output
Open-drain output LED1 pulls low to indicate charge status. When inactive, the output is high impedance. LED1
displays the state of charge and the charge results. The LED1 pin drives low in a 1Hz, 50% duty cycle “blink”
pattern to indicate cells are charging. LED1 blinks at 4Hz, 50% duty cycle to signal a charging fault has occurred.
The LED1 pin remains in a high-impedance state when no cells are present or the discharge latch is set. Table 2
summarizes the LED operation for each charge condition.
Table 2. LED DISPLAY PATTERNS BASED ON CHARGE STATE
High-Z = High Impedance
CURRENT REGULATION
Three basic modes of charging operation are supported by the DS2715: Offline switching through an optocoupler,
linear regulation, and DC input switched mode. The offline switching method requires a voltage clamp on the
regulated output. Mode of operation is selected through the Mode pin. Connecting the Mode pin to V
the analog block as a transconductance amplifier for linear mode of operation. Connecting the Mode pin to the
Cbias pin configures the DS2715 as a comparator for switched mode of operation.
Current-Sense Amplifier Mode
An error amplifier block provides several options to regulate the charge current. The 20mA open-drain output V
can drive a PMOS or PNP pass element for linear regulation, or the output can drive an optocoupler for isolated
feedback to a primary-side PWM controller. PMOS is the preferred device type when the pass element will also be
used as a discharge path to the load. This is because sufficient transconductance with both polarities of drain
current is easily realized compared to the difficulty in achieving this with BJT types. The SNS- pin is a remote-
sense return and should be connected to the battery ground side of the sense resistor using a separate isolated
conductor. During FAST-CHARGE, an error signal between the current-sense signal (across the sense resistor)
and the internal reference is produced so the voltage across the sense resistor is maintained at V
loop circuit. During PRECHARGE and TOPOFF, the voltage across the sense resistor is maintained at V
Current-Sense Comparator Mode
The comparator in the DS2715 switches the open drain V
voltage reaches high and low thresholds. The V
enabling the use of a switch-mode power stage. PMOS is again preferred when the pass element will also be used
LED1
BATTERY
High-Z
NO
DDD
50% duty cycle
Blinks at 1HZ,
. The DS2715 remains in DISCHARGE mode until a charge current across the
CHARGING
CH
output is capable of driving a PNP bipolar or a PMOS transistor,
CHARGE STATE
DCHG-RST
9 of 17
High-Z
DONE
T
pin. The state machine and all timers are reset to their
CH
or the device is power cycled. When either of these
pin between ON and OFF when the sense resistor
DCHG-SET
50% duty cycle
Blinks at 4Hz,
FAULT
or greater across the sense resistor,
DISCHARGE
MODE
High-Z
CH
pin is driven low
FC
SS
in a closed-
TO
configures
.
CH