ISL9205, ISL9205A, ISL9205B, ISL9205C, ISL9205D

FN9252 Rev 3.00

Page 13 of 17

September 30, 2016

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:

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 will never be 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 will stop and indicate 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

will be 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

pluses 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

150mA.

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 transient during a hot-plug event. A

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

damping to the voltage transient. 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 6.

State Machine 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. There are two paths to exit the trickle

charge, one is when the battery voltage rises above the

preconditioning charge threshold within the 1/8 TIMEOUT

interval, and the other is when the 1/8 TIMEOUT interval has

been elapsed before reaching the preconditioning charge voltage

threshold. When TIMEOUT fault occurs, the charger enters the

TIMEOUT fault state. There are only two ways to exit the TIMEOUT

fault state, by toggling the EN input or 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 will turn to logic low to

indicate charging again.