EVALPM6680 STMicroelectronics, EVALPM6680 Datasheet - Page 28

• Manufacturer Part Number: EVALPM6680
• Description: BOARD EVALUATION FOR PM6680
• Manufacturer: STMicroelectronics

Specifications of EVALPM6680

• Mfg Application Notes: PM6680 Eval Kit, AN2566 App Note
• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 3, Non-Isolated
• Power - Output: 13.25W
• Voltage - Output: 1.05V, 1.5V, 5V
• Current - Output: 5A, 5A, 100mA
• Voltage - Input: 6 ~ 28V
• Regulator Topology: Buck
• Frequency - Switching: 200kHz, 300kHz
• Board Type: Fully Populated
• Utilized Ic / Part: PM6680
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6241

Device description
7.7
28/49
Where RSNS is the sensing element (R
PM6680 provides also a fixed negative peak current limit to prevent an excessive reverse
inductor current when the switching section sinks current from the load in PWM mode. This
negative current limit threshold is measured between PHASE and SGND pins, comparing
the magnitude drop on the PHASE node during the conduction time of the low side
MOSFET with an internal fixed voltage of 120 mV.
If the current is sensed on the low side MOSFET, the negative valley-current limit I
device works in PWM mode) is given by:
Equation 9
Soft start and soft end
Each switching section is enabled separately by asserting high EN1/EN2 pins respectively.
In order to realize the soft start, at the startup the overcurrent threshold is set 25 % of the
nominal value and the undervoltage protection (see related sections) is disabled. The
controller starts charging the output capacitor working in current limit. The overcurrent
threshold is increased from 25 % to 100 % of the nominal value with steps of 25 % every
700 µs (typ.). After 2.8 ms (typ.) the undervoltage protection is enabled. The soft start time is
not programmable. A minimum capacitor CINT is required to ensure a soft start without any
overshoot on the output:
Equation 10
Figure 35. Soft start waveforms
Switching output
Current limit threshold
EN1/EN2
C
INT
≥
I
NEG
DSon
I
Lvalley
4
=
6
)
120
uA
R
+
DSon
∆
mV
2
I
L
×
C
out
Time
NEG
PM6680
(if the