STEVAL-ISA053V1 STMicroelectronics, STEVAL-ISA053V1 Datasheet - Page 23

• Manufacturer Part Number: STEVAL-ISA053V1
• Description: BOARD EVALUATION FOR PM6680
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of STEVAL-ISA053V1

• Design Resources: STEVAL-ISA053V1 Gerber Files PM6680 Eval Kit Schematic STEVAL-ISA053V1 Bill of Material
• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 3, Non-Isolated
• 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
• Input Voltage: 6 V to 28 V
• Output Voltage: 5 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: PM6680
• Kit Application Type: Power Management - Voltage Regulator
• Application Sub Type: Step Down DC/DC Controller
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: PM6680
• Other names: 497-6378

PM6680
7.2
Constant on time architecture
Figure 29
off-time constrain (300 ns typ.) is introduced to allow inductor valley current sensing on
synchronous switch. A minimum on-time (70 ns) is also introduced to assure the start-up
switching sequence.
PM6680 has a one-shot generator for each power section that turns on the high side
MOSFET when the following conditions are satisfied simultaneously: the PWM comparator
is high, the synchronous rectifier current is below the current limit threshold, and the
minimum off-time has timed out.
Once the on-time has timed out, the high side switch is turned off, while the synchronous
switch is turned on according to the anti-cross conduction circuitry management.
When the negative input voltage at the PWM comparator
down replica of the output voltage (see the external R1/R2 divider in
valley limit (determined by internal reference Vr = 0.9 V), the low-side MOSFET is turned off
according to the anti-cross conduction logic once again, and a new cycle begins.
Figure 29. Constant on-time block diagram
CSENSE
CSENSE
CSENSE
CSENSE
COMP
COMP
COMP
COMP
SKIP
SKIP
SKIP
SKIP
OUT
OUT
OUT
OUT
VIN
VIN
VIN
VIN
FB
FB
FB
FB
shows the simplified block diagram of a Constant On Time controller. A minimum
Positive
Positive
Positive
Positive
Current
Current
Current
Current
Limit
Limit
Limit
Limit
Vr
Vr
Vr
Vr
gm
gm
gm
gm
Vr
Vr
Vr
Vr
+
+
+
+
+
-
-
-
+
+
Comparato
Comparato
Comparato
Comparato
-
-
PWM
PWM
PWM
PWM
r
r
r
r
0.5V
0.5V
+
+
Toff
Toff
+
+
Toff
Toff
Zero-
Zero-
Zero
Zero
-
-
-
-
Comp.
Comp.
Comp.
Comp.
Ton
Ton
Ton
Ton
-
-
-
-
-
-
min
min
min
min
cross.
cross.
cross.
cross.
S
S
R
R
Q
Q
Q
Q
S
S
R
R
Q
Q
(Figure
LDO5
LDO5
+
+
+
LDO5
LDO5
-
-
-
0.5V
0.5V
0.5V
29), which is a scaled-
Level
Level
Level
Level
shifte
shifte
shifte
shifte
r
r
r
r
Figure
bandga
bandga
bandga
bandga
1.236V
1.236V
1.236V
1.236V
p
p
p
p
Vr
Vr
Vr
Vr
Device description
+
+
+
-
-
-
29), reaches the
HS
HS
HS
HS
driver
driver
driver
driver
LS
LS
driver
driver
LS
LS
driver
driver
LDO5
LDO5
LDO5
LDO5
0.25V
0.25V
0.25V
HGATE
HGATE
HGATE
HGATE
PHASE
PHASE
LGATE
LGATE
LGATE
LGATE
PGND
PGND
PGND
PGND
VREF
VREF
VREF
VREF
BOOT
BOOT
PHASE
PHASE
BOOT
BOOT
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