BL0921

BL0921

BL0921

BL0921

http://www.belling.com.cn

- 11 -

3/15/2007

Total 13 Pages

Single Phase Energy Meter IC

Single Phase Energy Meter IC

Single Phase Energy Meter IC

Single Phase Energy Meter IC

with Integrated Oscillator

with Integrated Oscillator

with Integrated Oscillator

with Integrated Oscillator

current

sampling

V1A

V1N

V1B

0V

V1A

V1B

V1B < 87.5% V1A

to ADC

FAULT

Figure 8. Fault Conditions for Inactive Input Less than Active Input

Figure 9 illustrates another fault condition. If V1A is the active input (i.e., is being used for billing)

and the voltage signal on V1B (inactive input) becomes greater than 114% of V1A, the FAULT

indicator goes active, and there is also a swap over to the V1B input. The analog input V1B has

now become the active input. Again there is a time delay of about 1.2 seconds associated with this

swap. V1A will not swap back to being the active channel until V1A becomes greater than 114%

of V1B. However, the FAULT indicator will become inactive as soon as V1A is within 12.5% of

V1B. This threshold eliminates potential chatter between V1A and V1B.

current

sampling

V1A

V1N

V1B

0V

V1A

V1B

V1A < 87.5% V1B

to ADC

FAULT

Figure 9. Fault Conditions for Inactive Input Greater than Active Input

Power Supply Monitor

The BL0921 contains an on-chip power supply monitor. If the supply is less than 4V±5% then

the BL0921 will go in an inactive state, i.e., no energy will be accumulated when the supply

voltage is below 4V. This is useful to ensure correct device operation at power up and during

power down. The power supply monitor has built-in hysteresis and filtering. This gives a high

degree of immunity to false triggering due to noisy supplies.

The trigger level is nominally set at 4V, and the tolerance on this trigger level is about ±5%. The

power supply and decoupling for the part should be such that the ripple at VDD does not exceed

5V±5% as specified for normal operation.

SLiM Technology

The BL0921 adopts the technology of SLiM (Smart Low current Management) to decrease the

static power greatly. The static power of BL0921 is about 15mW. This technology also decreases

the request for power supply design.

BL65XX series products used 0.35um CMOS process. The reliability and consistency are

advanced.

OPERATION MODE

Transfer Function

The BL0921 calculates the product of two voltage signals (on Channel 1 and Channel 2) and then