4 - Short Circuit Protection It is possible to protect L9936 against short circuit to ground and across the motor in the full bridge application. The circuit schematics shown in Fig. 4 uses two voltage comparators (UIA, UIB) to detect the Vce of the upper power transistors. U2A and U2B are open drain NAND gates (i.e. part no. HCC40107) and U3NBICID are non in- verting buffer to drive the two L9936 (i.e. part no. 74HC4050). UIA and UIB sense the differential voltage VD-OUTL and VD-OUTR respectively. Referring to Fig. 4, chosen Rl=lOOK and R2 = 20K, the values of R3 and R4 may be calculated ac- cording to the following formula:
| l | | | | ill ill l II | 11IIiI.:..I .llllllli!l III [ I I [ llil |
| | | | | {l l | | l I l Iii'! |
| | | | | I I! | Trij |
| | | | | i | | -5v | ili |
| | | | | | II | I | liI |
| | | | | | | | | l | II |
| | | | | | | | | I | lI |
| | | | | | | | J | II lI IIII |
| | | | | | | | | | l |
| | | | | | | | | | 1 |
| | | | | | | | | |
