KA35S280 View Datasheet(PDF) - Kasin Electronics Corporation

Part Name

Description

Manufacturer

KA35S280

Lead-Acid Battery Charger

Kasin Electronics Corporation 

KA35S280/281

Lead-Acid Battery Charger

- Pulsed-current charge

This algorithm consists of three phases (figure 6):

1. Phase1 - Qualification: The charging current is limited at ICOND (=IMAX/5) until the cell

voltage rises to VTH to prevent battery damage. In this condition The KA35S28X enters

the Charge Pending state and waits until the battery voltage rises to VTH. Charge

Pending is annunciated by LED0 and LED3 flashing.

2. Phase2 - Fast Charge: The charging current is regulated at IMAX (1.25 IMAX when faster

pin is 0) until the cell voltage rises to VBLK.

3. Phase3 - Maintenance: Charging current is removed until the battery voltage falls to

VFLT; charging current is then restored and regulated at IMAX (1.25 IMAX when faster pin is

0) until the battery voltage once again rises to VBLK. This cycle is repeated indefinitely.

Phase 3

I MAX

Current

Maintenance

VBLK

VFLT

Voltage

VTH

Phase 2

I COND

I MIN

I FLT

Phase 1

Fast Charge

Time

Figure 6 – Fast Charge

- Temperature monitoring

- Temperature compensation

The KA35S28X senses temperature by monitoring the voltage of TEMP pin. The KA35S28X

assumes a Negative Temperature Coefficient (NTC) thermistor, so the voltage on the TEMP

pin is inversely proportional to the temperature (see Figure 7). The temperature thresholds

used by the KA35S28X and their corresponding TEMP pin voltage are:

TCO Temperature Cut-Off: Higher limit of the temperature range in which charging is

allowed. VTCO = 0.12 * VCC.

HTF High-Temperature Fault: Threshold to which temperature must drop after

Temperature Cut-Off is exceeded before charging can begin again. VHTF = 0.15 *

VCC

LTF Low-Temperature Fault: Lower limit of the temperature range in which charging is

allowed. VLTF = 0.35 * VCC.

A resistor-divider network must be implemented that presents the defined voltage levels to

the TEMP pin at the desired temperatures (see Figure 8). The equations for determining

RT1 and RT2 are:

Equation 1:

Equation 2:

Where:

RLTF = Thermistor resistance at LTF

RHTF = Thermistor resistance at HTF

1% resistors are recommended. As an example, the resistor values for several temperature

windows computed for a 3KΩ thermistor are shown in Table 7.

2011 Nov 18

© 2011 Kasin Technology Inc.

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