EVAL6730 STMicroelectronics, EVAL6730 Datasheet - Page 4

• Manufacturer Part Number: EVAL6730
• Description: EVAL BOARD FOR L6730XX
• Manufacturer: STMicroelectronics
• Type: Motor / Motion Controllers & Driversr

Specifications of EVAL6730

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Power - Output: 66W
• Voltage - Output: 3.3V
• Current - Output: 20A
• Voltage - Input: 4.5 ~ 14V
• Regulator Topology: Buck
• Frequency - Switching: 400kHz
• Board Type: Fully Populated
• Utilized Ic / Part: L6730
• Input Voltage: 8 V to 52 V
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: L6208
• Other names: 497-5501

AN1451 APPLICATION NOTE
above V
as the current reverses direction and flows into the bulk capacitor. It turns out that, in fast decay, the highest
differential voltage is observed between the two OUT pins of the same bridge, at the beginning of the off-time,
and this must always be kept below 60V [3]. The same high voltage condition exists when a step is made and
the direction of current flow reverses in the bridge.
Figure 3. Currents and voltages during the dead time at the beginning of the off-time .
Figure 4 shows the voltage waveforms at the two OUT pins referring to a possible practical situation, with a peak
output current of 2.8A, V
ground spike amplitude is -2.65V for one output; the other OUT pin is at about 57V. In these conditions, total
differential voltage reaches almost 60V, which is the absolute maximum rating for the DMOS. Keeping differen-
tial voltage between two Output pins belonging to the same Full Bridge within rated values is a must that can
be accomplished with proper selection of Bulk capacitor value and equivalent series resistance (ESR), accord-
ing to current peaks and chopping style and adopting good layout practices to minimize PCB parasitic induc-
tances (see below) [3].
4/43
S
, due to the PCB inductance and voltage drop across the high-side (integrated) freewheeling diode,
Equivalent Circuit
Bulk Capacitor
S
= 52V, R
ESR
ESL
SENSE
R
PCB Parasitic
Inductance
SENSE
= 0.33 , T
*I+V
R
SENSE
F(Diode)
*I
J
SENSE
= 25°C (approximately) and a good PCB layout. Below
V
R
S
SENSE
High Differential Voltage
PCB Parasitic
Inductance
Dangerous
OUT
OUT
2
1
V
S
+V
F(Diode)