19-0796; Rev 0; 4/07
KIT
ATION
EVALU
E
BL
AVAILA
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
General Description
The MAX8664 dual-output PWM controller is a low-cost,
high-performance solution for systems requiring dual
power supplies. It provides two individual outputs that
operate 180° out-of-phase to minimize input current
ripple, and therefore, capacitance requirements. Built-in
drivers are capable of driving external MOSFETs to
deliver up to 25A output current from each channel.
The MAX8664 operates from a 4.5V to 28V input volt-
age source and generates output voltages from 0.6V
up to 90% of the input voltage on each channel. Total
output regulation error is less than ±0.8% over load,
line, and temperature.
The MAX8664 operates with a constant switching fre-
quency adjustable from 100kHz to 1MHz. Built-in boost
diodes reduce external component count. Digital soft-
start eliminates input inrush current during startup. The
second output has an optional external REFIN2, facili-
tating tracking supply applications. Each output is
capable of sourcing and sinking current, making the
device a great solution for DDR applications.
The MAX8664 employs Maxim’s proprietary peak volt-
age-mode control architecture that provides superior
transient response during either load or line transients.
This architecture is easily stabilized using two resistors
and one capacitor for any type of output capacitors. Fast
transient response requires less output capacitance,
consequently reducing total system cost. The MAX8664B
latches off both controllers during a fault condition, while
the MAX8664A allows one controller to continue to func-
tion when there is a fault in the other controller.
Features
o
±0.8% Output Accuracy Over Load and Line
o
Operates from a Single 4.5V to 28V Supply
o
Simple Compensation for Any Type of Output
Capacitor
o
Internal 6.5V Regulator for Gate Drive
o
Integrated Boost Diodes
o
Adjustable Output from 0.6V to 0.9 x V
IN
o
Digital Soft-Start Reduces Inrush Current
o
100kHz to 1MHz Adjustable Switching
o
180° Out-of-Phase Operation Reduces Input
Ripple Current
o
Overcurrent and Overvoltage Protection
o
External Reference Input for Second Controller
o
Prebiased Startup Operation
MAX8664
Ordering Information
PART
MAX8664AEEP+
MAX8664BEEP+
PIN-
PACKAGE
20 QSOP
20 QSOP
PKG
CODE
E20-1
E20-1
FAULT
ACTION
Independent
Joint
Note:
This device operates over the -40°C to +85°C operating
temperature range.
+Denotes
lead-free package.
Typical Operating Circuit
IN2
OUT2
IN
ILIM2
DH2
BST2
LX2
DL2
VL
ILIM1
DH1
BST1
LX1
IN1
OUT1
Applications
Desktop and Notebook PCs
Graphic Cards
ASIC/CPU/DSP Power Supplies
Set-Top Box Power Supply
Printer Power Supply
Network Power Supply
POL Power Supply
DL1
MAX8664
GND
FB2
REFIN2
V
CC
PGND
FB1
PWRGD
OSC/EN12
Pin Configuration appears at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For pricing delivery, and ordering information please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
MAX8664
ABSOLUTE MAXIMUM RATINGS
IN to GND ...........................................................…-0.3V to +30V
VL to GND...................................................................-0.3 to +8V
IN, BST_ to VL ........................................................-0.3V to +30V
V
CC
, FB_, PWRGD to GND.......................................-0.3V to +6V
VL to VCC ....................................................................-2V to +8V
PGND to GND .......................................................-0.3V to +0.6V
DL_ to PGND...............................................-0.3V to (V
VL
+ 0.3V)
DH_ to PGND............................................-0.3V to (V
BST_
+ 0.3V)
BST_ to GND.............................................................-0.3V to 38V
BST_ to LX ................................................................-0.3V to +8V
LX_ to PGND .................-1V (-2.5V for < 50ns transient) to +30V
DH_ to LX_................................................-0.3V to (V
BST_
+ 0.3V)
Note 1:
Package mounted on a multilayer PCB.
ILIM_ to GND ...............................................-0.3V to (V
IN
+ 0.3V)
ILIM_ to LX_............................................................-0.6V to +30V
OSC/EN12, REFIN2 to GND .....................-0.3V to (V
VCC
+ 0.3V)
VL Continuous Current ..............................................125mARMS
V
CC
Continuous Current..............................................10mARMS
Continuous Power Dissipation (T
A
= +70°C) (Note 1)
20-Pin QSOP (derate 11.0mW/°C above +70°C).........884mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
IN
= 12V, R
OSC/EN12
to GND = 56.1kΩ, REFIN2 = V
CC
, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at
T
A
= +25°C.) (Note 2)
PARAMETER
SUPPLY VOLTAGES
IN Supply Voltage
VL Output Voltage
V
CC
Output Voltage
V
CC
Undervoltage Lockout
(UVLO)
Standby Supply Current
Operating Supply Current
REGULATOR SPECIFICATIONS
Reference Accuracy
T
A
= 0°C to +85°C
T
A
= -40°C to +85°C
V
REFIN2
= V
VCC
V
REFIN2
= 1.000V
REFIN2 to Internal Reference
Switchover Threshold
REFIN2 Maximum Program Voltage
REFIN2 Disable Threshold
FB Input Bias Current
REFIN2 Bias Current
FB Propagation Delay
V
FB
= 0.5V
V
REFIN2
= 0.65V
FB rising to DH falling
Not to be switched during operation
T
A
= 0°C to +85°C
T
A
= -40°C to +85°C
0.5955
0.5930
0.5952
0.5925
0.995
2
0.600
0.600
0.600
0.600
1.000
V
VCC
-
0.7
1.3
50
3
3
90
0.6045
0.6070
0.6048
0.6075
1.005
V
VCC
-
0.3
V
V
mV
nA
nA
ns
V
V
7.2
IN = VL = V
CC
7.2V < V
IN
< 28V, 0 < I
VL
< 60mA
7.2V < V
IN
< 28V, 0 < I
CC
< 5mA
Rising
Hysteresis
OSC/EN12 not
connected
No switching,
V
FB_
= 0.65V
V
IN
= 12V, I
IN
V
CC
= V
IN
= V
VL
= 5V, I
IN
+ I
VL
+ I
VCC
V
IN
= 12V, I
IN
V
CC
= V
IN
= V
VL
= 5V, I
IN
+ I
VL
+ I
VCC
4.5
6.10
4.5
3.4
6.6
5.0
3.5
350
0.095
0.08
1.4
1.1
0.2
0.2
2.5
1.8
28.0
5.5
6.75
5.5
3.6
V
V
V
V
mV
mA
mA
CONDITIONS
MIN
TYP
MAX
UNITS
FB_ Regulation Accuracy
2
_______________________________________________________________________________________
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V, R
OSC/EN12
to GND = 56.1kΩ, REFIN2 = V
CC
, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at
T
A
= +25°C.) (Note 2)
PARAMETER
PROTECTION FEATURES
Overvoltage Protection (OVP)
Threshold
V
FB1
rising
V
FB2
rising, V
REFIN2
≤
1.3V
V
REFIN2
= V
VCC
, V
FB_
rising, MAX8664B
Power-Good (PWRGD) Threshold
High-Side Current-Sense Program
Current (Note 3)
ILIM Leakage
High-Side Current-Sense
Overcurrent Trip Adjustment Range
Internal Soft-Start Time
REFIN2 Internal Pulldown Resistance
Thermal-Shutdown Threshold
DRIVER SPECIFICATIONS
Sourcing current,
I
DH
= -50mA
Sinking current,
I
DH
= 50mA
Sourcing current,
I
DL
= -50mA
Sinking current,
I
DL
= 50mA
Dead Time for Low-Side to
High-Side Transition
DH_ Minimum On-Time
BST Current
Internal Boost Switch Resistance
PWM CLOCK OSCILLATOR
PWM Clock-Frequency Accuracy
PWM Clock-Frequency Adjustment
Range
OSC/EN12 Disable Current
R
OSC/EN12
= 226kΩ to 22.6kΩ
-15
100
1.5
+15
1000
2.5
%
kHz
µA
V
BST
- V
LX
= 7V, V
LX
= 28V, V
FB_
= 0.55V
OSC/EN12 not connected
DL_ falling to DH_ rising
V
VL
= 6.5V
V
IN
= V
VL
= V
VCC
= 5V
V
VL
= 6.5V
V
IN
= V
VL
= V
VCC
= 5V
V
VL
= 6.5V
V
IN
= V
VL
= V
VCC
= 5V
V
VL
= 6.5V
V
IN
= V
VL
= V
VCC
= 5V
V
VL
= 6.5V
V
VL
= 5V
70
13
1.35
1.55
0.9
1.0
1.3
1.5
0.6
0.7
25
28
108
1.25
0.001
6
149
2.3
43
ns
ns
mA
µA
Ω
1.1
2
Ω
1.4
2.1
Ω
R
OSC/EN12
= 56.1kΩ, 400kHz
Engaged momentarily at startup
Junction temperature
V
FB1
rising, MAX8664A
Hysteresis
T
A
= +85
o
C
T
A
= +25 C
T
A
= +25°C
T
A
= +85°C
0.05
2.5
10
+160
20
o
MAX8664
CONDITIONS
MIN
TYP
0.75
REFIN2
+ 0.15
MAX
UNITS
V
0.500
0.525
5
60
0.550
V
%
44
50
0.1
0.1
60
1.0
µA
µA
V
ms
Ω
°C
0.40
DH_ Driver Resistance
DL_ Driver Resistance
Note 2:
Specifications at -40°C are guaranteed by design and not production tested.
Note 3:
This current linearly compensates for the MOSFET temperature coefficient.
_______________________________________________________________________________________
3
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
MAX8664
Typical Operating Characteristics
(Circuit of Figure 2, 600kHz, V
IN
= 12V, V
OUT1
= 2.5V, V
OUT2
= 1.8V, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(600kHz, FIGURE 2)
MAX8664 toc01
EFFICIENCY vs. LOAD CURRENT
(1MHz, FIGURE 4)
MAX8664 toc02
LOAD REGULATION
(600kHz, FIGURE 2)
2.54
2.53
OUT1 VOLTAGE (%)
2.52
2.51
2.50
2.49
2.48
2.47
2.46
2.45
0
2
4
6
8
10
OUT1 LOAD CURRENT (A)
I
OUT2
= 0A
I
OUT2
= 8A
I
OUT2
= 4A
MAX8664 toc03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
LOAD CURRENT (A)
NO LOAD ON THE
OTHER REGULATOR
V
OUT
= 1.8V
V
OUT
= 2.5V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
V
IN
= 3.3V
V
VL
= 5V
NO LOAD ON OUT2
0.1
1
LOAD CURRENT (A)
V
OUT1
= 1.8V
V
OUT1
= 2.5V
2.55
10
10
LINE REGULATION
(600kHz, FIGURE 2)
2.54
2.53
OUT1 VOLTAGE (%)
2.52
2.51
2.50
2.49
2.48
2.47
2.46
2.45
6
8
10
12
14
16
18
20
INPUT VOLTAGE (V)
0
NO LOAD
50
8A LOAD
MAX8664 toc04
R
OSC/EN12
vs. SWITCHING FRQUENCY
MAX8664 toc05
OUT1 LOAD TRANSIENT (FIGURE 2)
MAX8664 toc06
2.55
250
200
R
OSC/EN12
(kΩ)
150
V
OUT2
100mV/div
100
I
OUT2
2.5A
5A
2.5A
2A/div
100
400
700
SWITCHING FREQUENCY (kHz)
1000
20μs/div
LOAD TRANSIENT
-3A TO +3A TO -3A (FIGURE 3)
MAX8664 toc07
POWER-UP WAVEFORMS
MAX8664 toc08
10V/div
V
OUT1
50mV/div
V
IN
2V/div
V
OUT2
+3A
I
OUT2
-3A
-3A
5A/div
V
PRWGD
100μs/div
1ms/div
50mV/div
V
OUT1
V
OUT2
5V/div
2V/div
4
_______________________________________________________________________________________
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
Typical Operating Characteristics (continued)
(Circuit of Figure 2, 600kHz, V
IN
= 12V, V
OUT1
= 2.5V, V
OUT2
= 1.8V, T
A
= +25°C, unless otherwise noted.)
MAX8664
POWER-DOWN WAVEFORMS
MAX8664 toc09
ENABLE WAVEFORMS (FIGURE 2)
MAX8664 toc10
V
IN
10V/div
V
OUT1
V
OUT2
2V/div
2V/div
V
PRWGD
5V/div
1ms/div
V
PRWGD
1ms/div
5V/div
V
OUT1
V
OUT2
2V/div
2V/div
ENABLE
5V/div
ENABLE WAVEFORMS (FIGURE 4)
MAX8664 toc11
SWITCHING WAVEFORMS
MAX8664 toc12
FEEDBACK VOLTAGE
vs. TEMPERATURE
604
MAX8664 toc13
605
10V/div
FEEDBACK VOLTAGE (mV)
ENABLE
5V/div
V
LX1
603
602
601
600
599
598
597
I
L1
V
OUT1
V
OUT2
1V/div
1V/div
V
LX2
I
L2
2μs/div
5A/div
10V/div
V
PRWGD
400μs/div
5V/div
5A/div
596
595
-40
-20
0
20
60
40
TEMPERATURE (°C)
NO LOAD
80
100
SHORT-CIRCUIT WAVEFORMS
MAX8664 toc14
OVERVOLTAGE PROTECTION
MAX8664 toc15
V
OUT1
V
OUT1
2V/div
I
IN
2A/div
I
L1
V
DH1
V
PRWGD
5A/div
5V/div
10μs/div
20μs/div
V
DL1
10V/div
10V/div
I
L1
10A/div
5V/div
_______________________________________________________________________________________
5
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