EVAL6730 STMicroelectronics, EVAL6730 Datasheet - Page 17

• 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

In some conditions (short off-time, very low regulated current, high motor winding L / R) the system may need
an on-time shorter than 1.5µs. In these cases the PWM current controller can loose the regulation.
Figure 17 shows the operation of the circuit in this condition. When the current first reaches the threshold, the
bridge is turned off for a fixed time and the current decays. During the following on-time current increases above
the threshold, but the bridge cannot be turned off until the minimum 1.5µs on-time expires. Since current in-
creases more in each on-time than it decays during the off-time, it keeps growing during each cycle, with steady
state asymptotic value set by duty-cycle and load DC resistance: the resulting peak current will be
I
where D = t
Figure 17. Minimum on-time can cause the PWM controller to loose the regulation.
pk
= V
S
· D / R
ON
LOAD
/ (t
ON
,
+ t
OFF
) is the duty-cycle and R
LOAD
is the load DC resistance.
needed t
is about 1.5 µs
minimum t
than 1.5 µs
ON
AN1451 APPLICATION NOTE
is less
ON
V
ref
/ R
SENSE
17/43