lb11947 Sanyo Semiconductor Corporation, lb11947 Datasheet - Page 6

• Manufacturer Part Number: lb11947
• Description: Pwm Current Control Type Dc Motor Driver + Switching Regulator
• Manufacturer: Sanyo Semiconductor Corporation

Descriptions of Each Function
(Switching regulator, over-current limit operation time chart)
The DC/DC over-current limit value is determined from the resistor connected between VBB and current sense pin.
Using about 75% from the upper threshold to lower threshold of the OSC triangular oscillation waveform and using the
mask circuit within the OSC charge section, the output of the over-current detection comparator is masked. This can
prevent detection error due to output switching noise.
When over-current flows through the output transistor, this over-current is detected if the ON width exceeding the over-
current detection threshold of IPSEN pin is more than the mask width. The counter is activated when over-current is
detected. If over-current is detected further after counting of four shots of OSC oscillation frequency, the output
transistor is turned OFF and latched in this condition. If no over-current is detected up to the eighth shot after counting
of four shots, the over-current condition is determined to be cancelled and the counter is reset, but the output transistor is
not turned OFF.
If the output transistor is latched to the OFF condition, recharge of VBB power supply causes canceling of the latch
condition.
VBB
VCC
CSS
IPSEN
OSC
Over-current
detection output
Logic RESET
Output OFF latch
Over-current
mask width
Over-current
detection threshold
Mask threshold level
Current limit value = 0.5(V)/RL
45V
5V
4V
Charge mask section
“HI” RESET
Output OFF latch cancelled
LB11947
Output OFF latch
VCC OFF
8V
1.3V
Latch canceling
Soft start
No. 7318 -6/14
9V