ng capacitor. The SD9057 works with both

The SD9057 does not require any output capacitor for

oltage-regulation phase. The SD9057 declares a

The SD9057 monitors the charging current during the v

The SD9057 is offered 8.4V output voltage.

9

Charge Termination Recharge

Battery Temperature Monitoring

A negative temperature coefficient (NTC) thermistor located close to the battery pack can be used to

monitor battery temperature and will not allow charging unless the battery temperature is within an

acceptable range.

Connect a 10k

Ω thermistor from the TS pin to ground. With the 85µA pull-up current source, the hot

temperature voltage threshold is 485mV. For cold temperature, the voltage threshold is set at 2.486V

with 85µA of pull-up current. The charge cycle begins or resumes once the temperature is within the

acceptable range.

Reverse Blocking Protection

The optional reverse-blocking protection diode, depicted in Figure1 provides protection from a faulted or

shorted input, or from a reversed-polarity input source. Without the protection diode, a faulted of shorted

input would discharge the battery pack through the body diode of the external pass transistor.

If a reverse-protection diode is incorporated in the design, it should be chosen to handle the fast charge

current continuously at the maximum ambient temperature. In addition, the reverse-leakage current of

the diode should be kept as small as possible.

Selecting Input Capacitor

In most applications, all that is high-frequency decoupli

regulated an unregulated external dc supplies. If a non-regulated supply is chosen, the supply voltage to

the minimum required input voltage at maximum load. If not, more capacitance must be added to the

input of the charger.

Selecting Output Capacitor

loop stability. In order to maintain good AC

stability in constant Voltage mode, a minimum capacitance of 10uF is recommenced to bypass the BAT

pin to GND. This capacitance provides compensation when there is no battery load. In addition, the

battery and interconnections appear inductive at high frequencies. These elements are in the control

feedback loop during Constant Voltage mode. Therefore, the bypass capacitance may be necessary to

compensate for the inductive nature of the battery pack.

Virtually any good quality output filter capacitor can be used, independent of the capacitor’s minimum

ESR (Effective Series Resistance) value. The actual value of the capacitor and its associated ESR

depends on the forward transconductance (gm) and capacitance of the external pass transistor. A 10uF

tantalum or aluminum electrolytic capacitor at the output is usually sufficient to ensure stability for up to

a 1A output current.

SD9057

Linear Li-Lon Battery Charger High Accuracy

Shouding

www.shouding.net