88PG8226A1-NFE1C000 Marvell, 88PG8226A1-NFE1C000 Datasheet - Page 19

• Manufacturer Part Number: 88PG8226A1-NFE1C000
• Manufacturer: Marvell

3
Figure 3: 88PG82XX Block Diagram
3.1
Copyright © 2008 Marvell
April 23, 2008, 2.00
Functional Description
Regulation and Start-up
The step-down switching regulator uses Pulse Width Modulation (PWM) and Pulse Frequency
Modulation (PFM) modes to regulate the output voltage using digital control. The mode of operation
depends on the level of output current and the output voltage.
In steady states, the step-down switching regulator monitors the current flowing through the inductor
to determine if the regulator is handling heavy or light load applications. For heavy load applications,
the step-down regulator operates in the PWM mode (B and C) to minimize the ripple current for
optimum efficiency and to minimize the ripple output voltage. The step-down regulator operates in
the PFM and Discontinuous Conduction Mode (DCM) (A and D) to limit the switching actions for
optimum efficiency in light load applications. In this mode, the average output voltage is slightly
higher than the average output voltage for heavy transient load applications.
OFF
ON
SDI
EN
10
10
REFERENCE
μ
μ
BAND-GAP
VOLTAGE
A
A
C1
PGood 1
SGND
CIRCUITRY
INTERNAL
SUPPLY
POWER
Interface
Serial
Data
Document Classification: Proprietary Information
EN 1
EN 2
SVIN
SHUTDOWN
THERMAL
VOLTAGE
LOCKOUT
UNDER-
A/D 1
150
°
OSCILLATOR
C
R1
A/D 1
A/D 2
FAULT
A/D 2
VSET1
DSP 1
R7
CIRCUITRY
RESISTOR
NETWORK
RESISTOR
DSP 1
DSP 2
SENSING
R8
PSET1
DSP 2
Current
Sense
PGood1
40us /40ms
C5
SFB1
CONTROL
CONTROL
PWM
PWM
+
-
VSET2
R5
SW2
PVIN2
Current
CIRCUITRY
RESISTOR
NETWORK
RESISTOR
Sense
SENSING
+
-
PSET2
R6
PGood 2
C2
40us /40ms
Functional Description
SFB1
PVIN2
Doc. No. MV-S103563-00 Rev. C
Regulation and Start-up
PVIN1
POR1
POR2
SW2
PGND2
SW1
SFB1
SFB2
PGND1
2.75V to 5.5V
L1
L2
Vin
Vin
R3
C3
C4
Page 19
Vout 2
Vout 1
VPOR