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MC33340EVK

Battery Fast Charge Controllers

ON Semiconductor 

MC33340 MC33342

Input Condition

Vsen Input Voltage:

>1.0 V and <2.0 V

>1.0 V and <2.0 V with

two consecutive –∆V

events detected after 160 s

<1.0 V or >2.0 V

Timer Backup:

Within time limit

Beyond time limit

Temperature Backup:

Within limits

Below lower limit

Above upper limit

Power Supply Voltage:

VCC >3.0 V and <18 V

VCC >0.6 V and <2.8 V

Figure 11. Controller Operating Mode Table

Controller Operation

The divided down battery pack voltage is within the fast charge voltage range. The charger switches from

trickle to fast charge mode as Vsen enters this voltage range, and a reset pulse is then applied to the

timer and the over temperature latch.

The battery pack has reached full charge and the charger switches from fast to a latched trickle mode.

A reset pulse must be applied for the charger to switch back to the fast mode. The reset pulse occurs

when entering the 1.0 V to 2.0 V window for Vsen or when VCC rises above 3.0 V.

The divided down battery pack voltage is outside of the fast charge voltage range. The charger switches

from fast to trickle mode.

The timer has not exceeded the programmed limit. The charger will be in fast charge mode if Vsen and

VCC are within their respective operating limits.

The timer has exceeded the programmed limit. The charger switches from fast to a latched trickle mode.

The battery pack temperature is within the programmed limits. The charger will be in fast charge mode if

Vsen and VCC are within their respective operating limits.

The battery pack temperature is below the programmed lower limit. The charger will stay in trickle mode

until the lower temperature limit is exceeded. When exceeded, the charger will switch from trickle to fast

charge mode.

The battery pack temperature has exceeded the programmed upper limit. The charger switches from fast

to a latched trickle mode. A reset signal must be applied and then released for the charger to switch back

to the fast charge mode. The reset pulse occurs when entering the 1.0 V to 2.0 V window for Vsen or

when VCC rises above 3.0 V.

This is the nominal power supply operating voltage range. The charger will be in fast charge mode if

Vsen, and temperature backup or timer backup are within their respective operating limits.

The undervoltage lockout comparator will be activated and the charger will be in trickle mode. A reset

signal is applied to the timer and over temperature latch.

Testing

Under normal operating conditions, it would take 283

minutes to verify the operation of the 34 stage ripple counter

used in the timer. In order to significantly reduce the test time,

three digital switches were added to the circuitry and are

used to bypass selected divider stages. Entering each of the

test modes without requiring additional package pins or

affecting normal device operation proved to be challenging.

Refer to the timer functional block diagram in Figure 12.

Switch 1 bypasses 19 divider stages to provide a 524,288

times speedup of the clock. This switch is enabled when the

Vsen input falls below 1.0 V. Verification of the programmed

fast charge time limit is accomplished by measuring the

propagation delay from when the Vsen input falls below 1.0 V,

to when the F/T output changes from a high–to–low state.

The 71, 106, 141, 177, 212, 247 and 283 will now correspond

to 8.1, 12.1, 16.2, 20.2, 24.3, 28.3 and 32.3 ms delays. It is

possible to enter this test mode during operation if the

equivalent battery pack voltage was to fall below 1.0 V. This

will not present a problem since the device would normally

switch from fast to trickle mode under these conditions, and

the relatively short variable time delay would be transparent

to the user.

Switch 2 bypasses 11 divider stages to provide a 2048

times speedup of the clock. This switch is necessary for

testing the 19 stages that were bypassed when switch 1 was

enabled. Switch 2 is enabled when the Vsen input falls below

1.0 V and the t1/Tref High input is biased at –100 mV.

Verification of the 19 stages is accomplished by measuring a

nominal propagation delay of 338.8 ms from when the Vsen

input falls below 1.0 V, to when the F/T output changes from

a high–to–low state.

Switch 3 is a dual switch consisting of sections “A” and “B”.

Section “A” bypasses 5 divider stages to provide a 32 times

speedup of the Vsen gate signal that is used in sampling the

battery voltage. This speedup allows faster test verification of

two successive –∆V events. Section “B” bypasses 11 divider

stages to provide a 2048 speedup of the trickle mode holdoff

timer. Switches 3A and 3B are both activated when the t1/Tref

High input is biased at –100 mV with respect to Pin 4.

8

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