STEVAL-ISA052V2 STMicroelectronics, STEVAL-ISA052V2 Datasheet - Page 27

• Manufacturer Part Number: STEVAL-ISA052V2
• Description: BOARD EVAL BASED ON PM6675A
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of STEVAL-ISA052V2

• Design Resources: STEVAL-ISA052V2 Gerber Files STEVAL-ISA052V2 Schematic STEVAL-ISA052V2 Bill of Material
• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 2, Non-Isolated
• Voltage - Output: 1.5V, 0.6 ~ 3.3V
• Voltage - Input: 4.5 ~ 36 V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: PM6675AS
• Input Voltage: 4.5 V to 36 V
• Output Voltage: 1.5 V
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Supplier Unconfirmed
• For Use With/related Products: PM6675AS
• Other names: 497-8413

PM6675AS
7.1.5
Current sensing and current limit
The PM6675AS switching controller employes a valley current sensing algorithm to properly
handle the current limit protection and the inductor current zero-crossing information. The
current is sensed during the conduction time of the low-side MOSFET. The current sensing
element is the low-side MOSFET on-resistance. The sensing scheme is visible in
Figure 30. Current sensing scheme
An internal 100 µA current source is connected to CSNS pin that is also the non-inverting
input of the positive current limit comparator. When the voltage drop developed across the
sensing parameter equals the voltage drop across the programming resistor R
controller skips subsequent cycles until the overcurrent is detected or the output UV
protection latches off the device (see par.
Referring to
efficiency applications.
It must be taken into account that the current limit circuit actually regulates the inductor
valley current. This means that RILIM must be calculated to set a limit threshold given by the
maximum DC output current plus half of the inductor ripple current:
Equation 21
where R
The PM6675AS provides also a fixed negative current limit to prevent excessive reverse
inductor current when the switching section sinks current from the load in forced-PWM (3rd
quadrant working conditions). This negative current limit threshold is measured between
PHASE and PGND pins, comparing the drop magnitude on PHASE pin with an internal
110mV fixed voltage.
SENSE
Figure 30
is the sensing device (R
, the RDSon sensing technique is tailored to all low cost, high
PGND
HGATE
PHASE
LGATE
CSNS
I
CL
=
DSon
100
R
Chapter 7.1.4
ILIM
).
µ
A
⋅
R
R
SENSE
ILIM
UV and OV Protections).
Device description
ILIM
Figure 30
, the
27/48
.