AN4243 datasheet(4/29 Pages) STMICROELECTRONICS

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Designing an application with the L6230

AN4243

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Doc ID 024199 Rev 1

Designing an application with the L6230

2.1

Current ratings

With MOSFET (DMOS) devices, unlike bipolar transistors, the current under short-circuit

conditions is, at first approximation, limited by the RDS(on) of the DMOS themselves and

could reach very high values.

The L6230 OUT pins and the two VSA and VSB pins are rated for a maximum of 1.4 A r.m.s

and 2.8 A peak (typical values). These values are meant to avoid damaging metal

structures, including the metallization on the die and bond wires.

In practical applications, maximum allowable current is less than these limits; actually the

constraint is the power dissipation. The device integrates overcurrent detection (OCD) that

provides protection against short-circuits between the outputs and between an output and

ground (see Section 2.10).

2.2

Voltage ratings and operating range

The L6230 requires a single supply voltage (VS), for the motor supply. Internal voltage

regulators provide the 5 V and 10 V required for the internal circuitry.

The operating range for VS is from 8 to 52 V. To prevent from working into undesirable low

voltage supply an undervoltage lockout (UVLO), circuit shuts down the device when supply

voltage falls below 6 V; to resume normal operating conditions, VS must then exceed 6.8 V.

The hysteresis is provided to avoid false intervention of the UVLO function during fast VS

ringings.

It should be noted, however, that DMOS's RDS(on) is a function of the VS supply voltage.

Actually, when VS is less than 10 V, RDS(on) is adversely affected, and this is particularly true

for the high-side DMOS that are driven from VBOOT supply. This supply is obtained through

a charge pump from the internal 10 V supply, which tends to reduce its output voltage when

VS goes below 10 V. Figure 2 shows the supply voltage of the high-side gate drivers

(VBOOT - VS) versus the supply voltage (VS).

Figure 2.

Supply voltage of high-side gate drivers versus supply voltage

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