ISL9205, ISL9205A, ISL9205B, ISL9205C, ISL9205D

FN9252 Rev 4.00

Page 12 of 17

Dec 20, 2018

Oscillator, TIMEOUT, and Charge Cycle

The ISL9205 family incorporates an oscillation circuit using an

external timing capacitor connected to the TIME pin. The

oscillator sets the limit for the maximum charge time during the

Trickle mode and the fast mode (CC and CV). The maximum

charge time (TIMEOUT) for the fast mode is set by:

TIMEOUT = 222tOSC

where the tOSC is the oscillator period. The minimum

programmable tOSC is 20µs (CTIME = 100pF). The time limit for the

trickle charge is 1/8 of the fast mode time limit. In the ISL9205

family, the timeout function can be disabled by pulling the TOEN pin

to logic LOW. When TIMEOUT is disabled, the charger is never

turned off in Constant Current and Constant Voltage modes. For the

ISL9205B and the ISL9105D, the timeout function is always

enforced. For the ISL9105A, there is not timeout function.

A charge cycle is the time interval between the time when the

charger is enabled to the moment it is disabled. If the battery

voltage is lower than the trickle charge threshold at the time the

charger is enabled, the charger enters the Trickle mode and the

timer is reset and its limit is set to 1/8 of TIMEOUT. If the timeout

function is enabled, the charger stops and indicates a TIMEOUT

fault if the charge time is longer than the limit. If the Trickle

mode completes successfully before the time limit, the charger

moves to CC mode and the timer is reset and the time limit is set

to TIMEOUT. The charger needs to reach the EOC conditions

before the TIMEOUT interval elapses, otherwise, a TIMEOUT fault

is issued. The charger indicates the EOC with the STATUS pin but

does not terminate charging.

Disabling TIMEOUT with TOEN

In the ISL9205 family, the timeout function in fast charge state

(CC/CV) can be disabled by pulling the TOEN pin to logic LOW.

The timeout function for the Trickle Charge mode can not be

disabled. Note that in the ISL9205A, there is no timeout function

for both the trickle and the CC/CV intervals, whereas in the

ISL9205 with TOEN set pulled to LOW, there is no timeout for the

CC/CV interval but the timeout function for the trickle interval is

still enforced.

Indications

The ISL9205 family has two open-drain status indication pins.

These two pins are FAULT and STATUS. These pins require an

external pull-up resistor to function properly. The V2P8 pin can be

used to indicate the presence of an AC adapter. When an adapter

pulses in, V2P8 is at 2.8V (logic Hi), otherwise V2P8 pin is at zero

voltage (logic Lo).

Charger Disable

The EN pin allows the user to disable the charger. When the charger

is disabled, all internal circuits are shut down and the quiescent

current at the input pin is less than a typical value of 150µA.

Remote Battery Voltage Sensing

In the ISL9205, ISL9205A, ISL9205B, and ISL9205C versions, a

Kelvin sense pin is provided for battery terminal voltage

monitoring. Thus, the IR drop due to the connection leads and

PCB traces can be eliminated, resulting in a more accurate battery

voltage monitoring, especially when the battery is located at a

significant distance away from the ISL9205. If remote sensing is

not needed, the VSEN pin can be connected to VBAT at the IC.

Applications Information

PCB Layout Guidance

The ISL9205 family uses thermally-enhanced QFN/DFN

packages that have an exposed thermal pad at the bottom side

of the package. The layout should connect as much as possible

to copper on the exposed pad. Typically, the component layer is

more effective in dissipating heat. The thermal impedance can

be further reduced by using other layers of copper connecting to

the exposed pad through a thermal via array. A minimum of four

such thermal vias are recommended. Each thermal via is

recommended to have 0.3mm diameter and 0.7mm distance

from other thermal vias.

Stability Consideration

The ISL9205 should behave like a current and thermal limited

linear regulator. The charger operation is stable with an output

ceramic decoupling capacitor in the range of 1µF to 200µF, with

or without a battery connected.

Input Bypass Capacitor

Due to the inductance of the power leads of the wall adapter or

USB source, the input capacitor type must be properly selected to

prevent high voltage transients during a hot-plug event. A

tantalum capacitor is a good choice for its high ESR, providing

damping to the voltage transients. Multi-layer ceramic capacitors,

however, have a very low ESR and hence, when chosen as input

capacitor, a 1Ω series resistor must be used to provide adequate

damping, as shown in the “Typical Applications” on page 5.

State Machine Diagram

The state machine diagram is shown in Figure 17 on page 13.

The diagram starts with the Power-Off state. When the input

voltage rises above the POR threshold, the charger resets itself.

Then, if the charger is disabled, the charger stays in the Charger

Disabled state. If the charger is enabled, the trickle charge starts.

At any time, when entering the trickle charge state, the internal

TIMEOUT timer is reset. Two paths to exit the trickle charge are:

• When the battery voltage rises above the preconditioning

charge threshold within the 1/8 TIMEOUT interval

• When the 1/8 TIMEOUT interval has been elapsed before

reaching the preconditioning charge voltage threshold

When a TIMEOUT fault occurs, the charger enters the TIMEOUT

fault state. Two ways to exit the TIMEOUT fault state are:

• Toggling the EN input

• Re-cycling the input power

If the charger finishes the trickle charger before the 1/8

TIMEOUT limit, it moves to the fast charge state. When entering

the fast charge state, the TIMEOUT timer is reset as well. If the

charger hits EOC conditions before the TIMEOUT, the charger

enters Charge Compete state. The charger stays on, but the

STATUS indicates EOC condition. When VBAT drops below the

recharge threshold, the STATUS pin turns to logic low to indicate

charging again.