STEVAL-ISA052V1 STMicroelectronics, STEVAL-ISA052V1 Datasheet - Page 23

• Manufacturer Part Number: STEVAL-ISA052V1
• Description: KIT EVAL PM6675S HE CTLR 2A REG
• Manufacturer: STMicroelectronics

Specifications of STEVAL-ISA052V1

• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 2, Non-Isolated
• Voltage - Output: 1.5V, 0.6 ~ 3.3V
• Current - Output: 10A, 2A
• Voltage - Input: 4.5 ~ 28 V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: PM6675
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-8426

PM6675S
7.1.2
Figure 34. Switching section simplified block diagram
VSEL
VSEL
COMP
COMP
COMP
COMP
VSEL
VSEL
VSNS
VSNS
VSNS
VSNS
CSNS
CSNS
CSNS
CSNS
Output ripple compensation and loop stability
The loop is closed connecting the center tap of the output divider (internally, when the fixed
output voltage is chosen, or externally, using the VSEL pin in the adjustable output voltage
mode). The feedback node is the negative input of the error comparator, while the positive
input is internally connected to the reference voltage (Vr = 0.6 V). When the feedback
voltage becomes lower than the reference voltage, the PWM comparator goes to high and
sets the control logic, turning on the high-side MOSFET. After the On-Time (calculated as
previously described), the system releases the high-side MOSFET and turns on the
synchronous rectifier.
The voltage drop along ground and supply PCB paths, used to connect the output capacitor
to the load, is a source of DC error. Furthermore the system regulates the output voltage
valley, not the average, as shown in
capacitor is an additional source of DC error. To compensate this error, an integrative
network is introduced in the control loop, by connecting the output voltage to the COMP pin
through a capacitor (C
Integrator
Integrator
Integrator
Integrator
100uA
100uA
100uA
100uA
Positive Current Limit comparator
Positive Current Limit comparator
Min
Min
counter
counter
Positive Current Limit comparator
Positive Current Limit comparator
Min
Min
counter
counter
Zero
Zero-
Zero
Zero-
Comparator
Comparator
Comparator
Comparator
0.6V
0.6V
0.6V
0.6V
VBG
VBG
VBG
VBG
fsw
fsw
fsw
fsw
-
-
gm
gm
gm
gm
crossing
crossing
crossing
crossing
PWM Comparator
PWM Comparator
PWM Comparator
PWM Comparator
+
+
+
+
-
-
-
-
+
+
S
S
R
R
_
_
VSEL<4V
VSEL<4V
INT
Q
Q
Q
Q
) as shown in
PULSE
PULSE
PULSE
PULSE
-
-
-
-
SKIP
SKIP
SKIP
SKIP
VOSC
VOSC
VOSC
VOSC
1-Shot generator
1-Shot generator
S
S
R
R
Ton-
Ton-
Ton
Ton
Toff
Toff-
Toff
Toff-
Figure 37
Ton
Ton
Ton
Ton
-
-
-
-
min
min
min
min
min
min
min
min
VSNS
VSNS
VSNS
VSNS
Figure 35
Q
Q
Q
Q
SGND
SGND
SGND
SGND
VOSC
VOSC
VOSC
VOSC
. Thus, the voltage ripple on the output
VOSC
VOSC
VOSC
VOSC
+
+
-
-
.
Anti cross-
Anti cross-
conduction
conduction
circuitry
circuitry
2.5V
2.5V
S
S
R
R
0.6V
0.6V
0.6V
0.6V
Q
Q
+
+
-
-
+
+
-
-
Level
Level
shifter
shifter
Level
Level
shifter
shifter
VREF
VREF
500mV
500mV
VREF
VREF
2.5V
2.5V
VBG
VBG
VBG
VBG
Device description
bandgap
bandgap
bandgap
bandgap
LS
LS
LS
LS
driver
driver
driver
driver
1.236V
1.236V
1.236V
1.236V
HS
HS
HS
HS
driver
driver
driver
driver
PHASE
PHASE
VCC
VCC
VCC
VCC
HGATE
HGATE
PHASE
PHASE
BOOT
BOOT
HGATE
HGATE
LGATE
LGATE
LGATE
LGATE
PGND
PGND
BOOT
BOOT
PGND
PGND
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