IR3522 International Rectifier, IR3522 Datasheet - Page 9

• Manufacturer Part Number: IR3522
• Description: DDR & VTT CONTROL IC
• Manufacturer: International Rectifier

www.DataSheet4U.com
SYSTEM THEORY OF OPERATION
PWM Control Method
The PWM block diagram of the xPHASE3
with trailing edge modulation is used to provide system control. A voltage type error amplifier with high-gain and
wide-bandwidth, located in the Control IC, is used for the voltage control loop. The feed-forward control is
performed by the phase ICs as a result of sensing the Input voltage (FET’s drain voltage). The PWM ramp slope
will change with the input voltage and automatically compensate for changes in the input voltage. The input voltage
can change due to variations in the silver box output voltage or due to the wire and PCB-trace voltage drop related
to changes in load current.
.
Frequency and Phase Timing Control
The system oscillator is located in the Control IC and is programmable from 250 kHz to 9 MHZ by an external
resistor. The control IC clock signal (CLKOUT) is connected to CLKIN of all the phase ICs. The phase timing of the
phase ICs is controlled by a daisy chain loop. The control IC phase clock output (PHSOUT) is connected to the
phase clock input (PHSIN) of the first phase IC, and PHSOUT of the first phase IC is connected to PHSIN of the
second phase IC, etc. The last phase IC (PHSOUT) is connected back to PHSIN of the control IC to complete the
loop. During power up, the control IC sends out clock signals from both CLKOUT and PHSOUT pins and detects
the feedback at PHSIN pin to determine the phase number and monitor any fault in the daisy chain loop. Figure 4
shows the phase timing for a four phase converter.
Page 9
IR3522 CONTROL IC
ERROR
AMPLIFIER
CLOCK GENERATOR
REMOTE SENSE
AMPLIFIER
+
-
VREF1_FAST
+
-
CLKOUT
PHSOUT
PHSIN
VOUT1
VREF1
LGND
EAOUT1
FB1
R CP1
C CP11
CC P12
R FB12
C FB1
GATE DRIVE
VOLTAGE
RF B11
Figure 3 - PWM Block Diagram
TM
architecture is shown in Figure 3. Feed-forward voltage mode control
PHSOUT
PHSOUT
IOUT
DACIN
IOUT
DACIN
CLKIN
PHSIN
CLKIN
PHSIN
EAIN
EAIN
3K
3K
VC CL
VC CL
C LK
D
C LK
D
SHARE ADJUST
ERROR AMPLIFIER
SHARE ADJUST
ERROR AMPLIFIER
Q
Q
+
-
+
-
RAMP
DISCHARGE
CLAMP
RAMP
DISCHARGE
CLAMP
ENABLE
ENABLE
IR3506 PHASE IC
IR3506 PHASE IC
PWM
COMPARATOR
-
PWM
COMPARATOR
-
VID6
VID6
+
+
VID6
VID6
VID6
VID6
-
+
-
+
+
-
+
-
PWM
LATCH
DOMINANT
PWM
LATCH
DOMINANT
S
RESET
R
S
RESET
R
VID6
VID6
VID6
VID6
+
+
+
+
CURRENT
SENSE
AMPLIFIER
CURRENT
SENSE
AMPLIFIER
+
-
+
-
VCCH
GATEH
SW
VCCL
GATEL
PGND
CSIN+
CSIN-
VCCH
GATEH
SW
VCCL
GATEL
PGND
CSIN+
CSIN-
C CS
C CS
R CS
R CS
C BST
C BST
V3.01
IR3522
COUT
VIN
VOSNS1+
VOUT1
GND
VOSNS1-