AN1451 datasheet(22/43 Pages) STMICROELECTRONICS

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AN1451 APPLICATION NOTE

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2.13.1 Maximum output current vs. selectable devices

Figure 22 reports a performance comparison between L6228 (std. power) and L6208 (high power) for different

packages, with the following assumptions:

- Normal Drive Mode (two-phase on)

- Supply voltage: 24 V; Switching frequency: 30 kHz.

- Tamb = 25 °C, TJ = 125 °C.

- Maximum RDS(ON) (taking into account process spread) has been considered, @ 125 °C.

- Maximum quiescent current IQ (taking into account process spread) has been considered.

- PCB is a FR4 with a dissipating copper surface on the top side of 6 cm2 (with a thickness of 35 µm) for

SO and PowerDIP packages (D, N suffixes).

- PCB is a FR4 with a dissipating copper surface on the top side of 6 cm2 (with a thickness of 35 µm), 16

via holes and a ground layer for the PowerSO package (PD suffix).

- For each device (on the x axis) y axis reports the maximum output current.

Figure 22. Maximum output current vs. selectable devices.

2.13.2 Power Dissipation Formulae for different sequences

Figure 23 to Figure 26 are screenshots of a spreadsheet that helps calculating power dissipation in specified

conditions (application and motor data), and estimates the resulting junction temperature for a given package

and copper area available on the PCB [6]. The model considers power dissipation during the on-time and the

off-time, taking into account the selected decay, rise and fall time (when a phase change occurs) considering

the operating sequence, the switching losses and the quiescent current power dissipation.

0.5 0

0.7 0

0.9 0

1.1 0

1.3 0

1.5 0

1.7 0

Load Current

[A]

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