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ISL6227EVAL1 DDR Evaluation Board Setup
Procedure
This document describes the setup procedure for the
ISL6227 Evaluation Board DDR implementation. For
information about the dual switcher application, please refer
to the ISL6227EVAL2 Evaluation Board Setup Procedure.
General Description
The ISL6227 can control two output voltages adjustable from
0.9V to 5.5V. The ISL6227 combines two synchronous PWM
voltage regulators into a single IC. When the DDR pin is set
to high, it transforms the IC into a complete DDR application.
Channel 1 can be set at a fixed 300kHz forced PWM mode or
an automatic mode with hysteretic diode-emulation at light
load and constant-frequency PWM synchronous rectification
at heavy load, assure high efficiency over a wide range of
conditions. Channel 2 is set at fixed 300kHz forced PWM
mode with synchronous rectification because of sinking
current requirement for DDR applications. Both channels use
the lower MOSFET r
DS(ON)
as the current sense element for
high efficiency operations. It is preferred that the input of the
second channel connects to the output of the first channel in
DDR applications.
Voltage-feed-forward ramp modulation, current mode control,
and internal feedback compensation provide fast response to
input voltage and output load transients.
ISL6227 monitors the output voltage of CH1 only by the
voltage on VSEN1 pin. PGOOD1 (power good) signal is
asserted after its soft-start sequence has completed, and the
output voltage within -11%/+15% of the set point. PGOOD2
pin is used to bring the VDDQ/2 into the chip as the
reference voltage of the second channel error amplifier.
Built-in overvoltage protection prevents the output from
going above 115% of the set point by holding the lower
MOSFET on and the upper MOSFET off. When the output
voltage decays below the overvoltage threshold, normal
operation automatically resumes. Once the soft-start
sequence has completed, undervoltage protection will latch
the channel off if the output drops below 75% of its set point
value. There is no overvoltage protection for Channel 2 in
DDR application.
Adjustable overcurrent protection (OCP) monitors the
voltage drop across the r
DS(ON)
of the lower MOSFET. If
more precise current-sensing is required, an external current
sense resistor may be used. The OCP threshold can be
adjusted by the resistor on OCSET pin and the current
sensing gain can be adjusted by the resistor from ISEN pin
to the phase node of the converter. Any overcurrent on the
second channel will be reflected to the first channel. There is
no OCP for the second channel.
In order to alleviate the interaction between the two channels
caused by the switching noise, a phase shift has been
implemented on the controller. If the input voltage is above
5V, the VIN pin should connect the input voltage. This would
provide the input voltage feed forward function and
command the second channel 90 degree lagging the first
channel. If the input voltage is at 3.3V, the VIN pin should
connect to ground. This would result in a fixed ramp for the
PWM comparator and command an in-phase operation of
the two channels.
Features
• Provides regulated output voltage in the range of 0.9V–5.5V
- High efficiency over wide load range
- Synchronous buck converter with hysteretic operation at
light load
- Selection of hysteretic/CCM mode on channel 1. Forced
CCM on channel 2 for DDR application
• Uses MOSFET r
DS(ON)
for current sensing or uses
current-sense resistor for precision overcurrent protection
• Overvoltage, undervoltage and overcurrent protection
• Undervoltage lock-out on VCC pin
• Dual input voltage mode operation
- Operates directly from battery 5V to 24V input
- Operates from 3.3V or 5V system rail
• Excellent dynamic response
- Combined voltage feed-forward and current mode
control
• Power-good signal for channel 1 in DDR application
Pinout
ISL6227 (28 LD SSOP)
TOP VIEW
Ordering Information
PART #
TEMP. (°C)
PACKAGE
PKG
DWG #
ISL6227CA
-10 to 100 28 Ld SSOP
M28.15
ISL6227CAZ
(Note)
-10 to 100 28 Ld SSOP (Lead-Free)
M28.15
ISL6227CA-T
-10 to 100 28 Ld SSOP Tape and Reel M28.15
ISL6227CAZ-T
(Note)
-10 to 100 28 Ld SSOP Tape and Reel
(Lead-Free)
M28.15
NOTE: Intersil Lead-Free products employ special lead-free material
sets; molding compounds/die attach materials and 100% matte tin
plate termination finish, which is compatible with both SnPb and lead-
free soldering operations. Intersil Lead-Free products are MSL
classified at lead-free peak reflow temperatures that meet or exceed
the lead-free requirements of IPC/JEDEC J Std-020B.
EN1
GND
DDR
VSEN1
VIN
PG1
VCC
VOUT1
ISEN1
LGATE1
PGND1
BOOT1
UGATE1
PHASE1
ISEN2
LGATE2
PGND2
BOOT2
UGATE2
PHASE2
EN2
VSEN2
VOUT2
OCSET2
OCSET1
SOFT1
SOFT2
PG2/REF
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1-888-INTERSIL or 321-724-7143
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Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2004. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note
June 2004
AN1067
Содержание ISL6227EVAL1
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