TPIC44H01DA datasheet(23/28 Pages) TI

23 / 28 page

TPIC44H01

4-CHANNEL SERIAL AND PARALLEL HIGH-SIDE PRE-FET DRIVER

SLIS088 – SEPTEMBER 1998

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

short-to-ground detection/protection

The TPIC44H01 provides short-to-ground detection to protect the external FET from a more severe condition

than an over-current condition. This is accomplished by engaging a reduced deglitch time should a

short-to-ground be detected, thereby turning off the FET faster than in an over-current condition. Figure 17

illustrates operation of the short-to-ground detection scheme. A short-to-ground is detected during on-state by

monitoring the condition of the low-side comparator in addition to the V(OVDS) comparator. If the low-side

comparator indicates SRCx voltage is below the V(STG) fault threshold voltage (2-Vbg referenced to ground),

a short-to-ground condition is detected. Should this condition exist for the entire duration of t(STG), a valid fault

is registered, causing the associated gate drive output to turn off, the FLT pin to latch low, and the appropriate

serial data fault bits to be set. Deglitch of short-to-ground detection relies on the over-current deglitch timer,

which begins if the FET VDS exceeds V(OVDS) (that is over-current event). However, detection of short-to-ground

reduces the deglitch time from t(OC) to t(STG), as shown in Table 4. The deglitch time allows V(SRCx) voltage to

stabilize after the FET is turned on, and to distinguish between normal and shorted loads.

As shown in Figure 17, three short-to-ground cases can occur.

Case 1: SRCx is shorted to ground prior to gate drive turn on. GATEx is shut off when t(STG) is reached.

Case 2: SRCx is shorted to ground after gate drive is turned on and V(SRCx) falls beneath V(STG) before

t(STG) is exceeded. Thus, t(STG) is initiated once V(SRCx) falls beneath V(OVDS) and GATEx is shut

off when t(STG) is reached.

Case 3: After gate drive is turned on, SRCx is pulled beneath V(OVDS),thenfallsbeneathV(STG)aftert(STG)

is reached. GATEx is not shut off when t(STG) is reached, but shuts off immediately when SRCx fall

beneath V(STG).

TPIC44H01DA Datasheet(PDF) 23 Page - Texas Instruments