19-2696; Rev 1; 4/07
KIT
ATION
EVALU
BLE
AVAILA
1.5MHz Dual 180° Out-of-Phase
PWM Step-Down Controller with POR
General Description
Features
♦
Low Output Noise in DSL Band
♦
Ceramic Input/Output Capacitors
♦
Step-Down or Step-Up/Step-Down Operation
♦
Four Output, 90-Degree Out-of-Phase Operation
(Using Two MAX8529s)
♦
Foldback Current Limit
♦
4.75V to 23V Input Supply Range
♦
0 to 18V Output Voltage Range (Up to 6A)
♦
> 90% Efficiency
♦
Fixed-Frequency PWM Operation
♦
Adjustable 600kHz to 1.5MHz Switching
Frequency
♦
External SYNC Input
♦
Clock Output for Master/Slave Synchronization
♦
Soft-Start and Soft-Stop
♦
RST
Output with 140ms Minimum Delay
♦
Lossless Current Limit (No Sense Resistor)
MAX8529
The MAX8529 dual, synchronized, step-down controller
generates two outputs from input supplies ranging from
4.75V to 23V. Each output is adjustable from sub-1V
to 18V. Input voltage ripple and total RMS input ripple
current are reduced by synchronized 180-degree out-of-
phase operation.
The switching frequency is adjustable from 600kHz to
1.5MHz with an external resistor. Alternatively, the con-
troller can be synchronized to an external clock gener-
ated to another MAX8529 or a system clock. One
MAX8529 can be set to generate an in-phase, or 90-
degree out-of-phase, clock signal for synchronization
with additional controllers. This allows two controllers to
operate either as an interleaved two- or four-phase sys-
tem with each output shifted by 90 degrees. These
devices also feature soft-start and soft-stop.
The MAX8529 eliminates the need for current-sense
resistors by utilizing the low-side MOSFET’s on-resis-
tance as a current-sense element. This protects the
DC-to-DC components from damage during output
overload conditions or when output short circuit faults
without requiring a current-sense resistor. Adjustable
foldback current limit reduces power dissipation during
short-circuit conditions. The MAX8529 includes a
power-on reset output to signal the system when both
outputs reach regulation.
The MAX8529 is available in a 24-pin QSOP package. An
evaluation kit is available to speed designs.
Ordering Information
PART
MAX8529EEG
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
24 QSOP
Applications
xDSL Modems and Routers
DSP, ASIC, and FPGA Power Supplies
Set-Top Boxes
Broadband Routers
TOP VIEW
COMP2 1
FB2 2
ILIM2 3
OSC 4
V+ 5
REF 6
GND 7
CKO 8
SYNC 9
ILIM1 10
FB1 11
COMP1 12
Pin Configuration
24 EN
23 DH2
22 LX2
21 BST2
20 DL2
MAX8529
19 V
L
18 PGND
17 DL1
16 BST1
15 LX1
14 DH1
13 RST
QSOP
________________________________________________________________
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.
1.5MHz Dual 180° Out-of-Phase
PWM Step-Down Controller with POR
MAX8529
ABSOLUTE MAXIMUM RATINGS
V+ to GND ..............................................................-0.3V to +25V
PGND to GND .......................................................-0.3V to +0.3V
V
L
to GND ..................-0.3V to the lower of +6V and (V+ + 0.3V)
BST1, BST2 to GND ...............................................-0.3V to +30V
LX1 to BST1..............................................................-6V to +0.3V
LX2 to BST2..............................................................-6V to +0.3V
DH1 to LX1 ..............................................-0.3V to (V
BST1
+ 0.3V)
DH2 to LX2 ..............................................-0.3V to (V
BST2
+ 0.3V)
DL1, DL2 to PGND........................................-0.3V to (V
L
+ 0.3V)
CKO, REF, OSC, ILIM1, ILIM2,
COMP1, COMP2 to GND ..........................-0.3V to (V
L
+ 0.3V)
FB1, FB2,
RST,
SYNC, EN to GND...........................-0.3V to +6V
V
L
to GND Short Circuit..............................................Continuous
REF to GND Short Circuit ...........................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
24-Pin QSOP (derate 9.4mW/°C above +70°C)...........762mW
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+ = 12V, EN = ILIM_ = V
L
, SYNC = GND, I
VL
= 0mA, PGND = GND, C
REF
= 0.22µF, C
VL
= 4.7µF (ceramic), R
OSC
= 10kΩ,
compensation components for COMP_ are from Figure 1, T
A
= -40°C to +85°C (Note 1), unless otherwise noted.)
PARAMETER
GENERAL
V+ Operating Range
V+ Operating Supply Current
V+ Standby Supply Current
Thermal Shutdown
Current-Limit Threshold
V
L
REGULATOR
Output Voltage
V
L
Undervoltage Lockout
Trip Level
REFERENCE
Output Voltage
Reference Load Regulation
SOFT-START
Digital Ramp Period
Soft-Start Steps
FREQUENCY
Low End of Range
High End of Range
DH_ Minimum Off-Time
R
OSC
= 10kΩ
R
OSC
= 5kΩ
R
OSC
= 5kΩ
540
1020
600
1200
110
600
1380
160
kHz
kHz
ns
Internal 6-bit DAC for one converter to ramp from 0V to
full scale (Note 3)
1024
64
DC-to-
DC
Clocks
Steps
I
REF
= 0µA
0µA < I
REF
< 50µA
1.98
0
2.00
4
2.02
10
V
mV
(Note 2)
V
L
= V+ (Note 2)
V
L
unloaded, no MOSFETs connected
EN = LX_ = FB_ = 0V
R
OSC
= 10kΩ
ILIM_ = V
L
PGND - LX_
R
ILIM_
= 100kΩ
R
ILIM_
= 600kΩ
5.5V < V+ < 23V, 1mA < I
LOAD
< 50mA
Rising temperature, typical hysteresis = 10°C
75
32
225
4.75
4.4
4.75
4.75
4.0
0.50
4.8
0.65
160
100
50
300
5
4.55
125
62
375
5.25
4.7
V
V
mV
23.00
5.50
7.0
1.00
V
mA
mA
°C
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
1.5MHz Dual 180° Out-of-Phase
PWM Step-Down Controller with POR
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 12V, EN = ILIM_ = V
L
, SYNC = GND, I
VL
= 0mA, PGND = GND, C
REF
= 0.22µF, C
VL
= 4.7µF (ceramic), R
OSC
= 10kΩ,
compensation components for COMP_ are from Figure 1, T
A
= -40°C to +85°C (Note 1), unless otherwise noted.)
PARAMETER
SYNC Range
SYNC Input Pulse Width
SYNC Rise/Fall Time
ERROR AMPLIFIER
FB_ Input Bias Current
FB_ Input Voltage Set Point
FB_ to COMP_ Transconductance
DRIVERS
DL_, DH_ Break-Before-Make Time C
LOAD
= 5nF
Low
DH_ On-Resistance
High
DL_ On-Resistance
LOGIC INPUTS (EN, SYNC)
Input Low Level
Input High Level
Input High/Low Bias Current
LOGIC OUTPUTS (CKO)
Output Low Level
Output High Level
COMP_
Pulldown Resistance During
Shutdown and Current Limit
RST
OUTPUT
Output-Voltage Trip Level
Output Low Level
Output Leakage
Reset Timeout Period
FB_ to Reset Delay
Both FBs must be over this to allow the reset timer to
start; there is no hysteresis
V
L
= 5V, sinking 3.2mA
V
L
= 1V, sinking 0.4mA
V+ = V
L
= 5V, V
RST
= 5.5V, V
FB
= 1V
V
FB_
= 1V
FB_ overdrive from 1V to 0.85V
140
315
4
0.87
0.9
0.93
0.4
0.3
1
560
V
V
µA
ms
µs
17
Ω
V
L
= 5V, sinking 5mA
V
L
= 5V, sourcing 5mA
4.0
0.4
V
V
Typical 15% hysteresis, V
L
= 4.75V
V
L
= 5.5V
V
EN
= 0 or 5.5V
2.4
-1
+0.1
+1
0.8
V
V
µA
Low
High
30
1.5
3
0.6
3
2.5
5
1.5
5
ns
Ω
Ω
0°C to +85°C
-40°C to +85°C
0.99
1.25
1.2
1.00
1.8
1.8
250
1.01
2.70
2.9
nA
V
mS
CONDITIONS
Internal oscillator nominal frequency must be set to half
of the SYNC frequency
(Note 3)
(Note 3)
High
Low
MIN
1000
100
100
100
TYP
MAX
2800
UNITS
kHz
ns
ns
MAX8529
Note 1:
Specifications to -40°C are guaranteed by design and not production tested.
Note 2:
Operating supply range is guaranteed by V
L
line regulation test. Connect V+ to V
L
for 5V operation.
Note 3:
Guaranteed by design and not production tested.
_______________________________________________________________________________________
3
1.5MHz Dual 180° Out-of-Phase
PWM Step-Down Controller with POR
MAX8529
Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= 6V, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD
MAX8529 toc01
OUTPUT VOLTAGE ACCURACY
vs. LOAD
MAX8529 toc02
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
LOAD (A)
OUT1
OUT2
1.0
OUTPUT VOLTAGE ACCURACY (%)
0.5
0
OUT1
OUT2
-0.5
10
-1.0
0
1
2
3
LOAD (A)
4
5
V
L
VOLTAGE ACCURACY
vs. LOAD CURRENT
MAX8529 toc03
SWITCHING FREQUENCY vs. R
OSC
MAX8529 toc04
0.5
1600
SWITCHING FREQUENCY (kHz)
0
V
L
VOLTAGE ACCURACY
1400
-0.5
1200
-1.0
1000
-1.5
800
-2.0
0
50
100
150
LOAD CURRENT (mA)
600
4
6
R
OSC
(kΩ)
8
10
LOAD TRANSIENT RESPONSE (OUTPUT 1)
MAX8529 toc05
LOAD TRANSIENT RESPONSE (OUTPUT 2)
MAX8529 toc06
V
OUT2
50mV/div
AC-COUPLED
V
OUT1
50mV/div
AC-COUPLED
I
OUT1
1A/div
0A
10μs/div
V
OUT1
50mV/div
AC-COUPLED
V
OUT2
50mV/div
AC-COUPLED
I
OUT2
1A/div
0A
10μs/div
4
_______________________________________________________________________________________
1.5MHz Dual 180° Out-of-Phase
PWM Step-Down Controller with POR
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
IN
= 6V, T
A
= +25°C, unless otherwise noted.)
SOFT-START AND SOFT-STOP WAVEFORM
MAX8529 toc07
MAX8529
RESET TIMEOUT
MAX8529 toc08
OUT-OF-PHASE WAVEFORM
MAX8529 toc09
5V
EN
0V
V
OUT2
1V/div
0V
V
OUT1
1V/div
0V
5V/div
5V
EN
0V
V
OUT2
2V/div
0V
V
OUT1
2V/div
0V
V
RST
0V
V
OUT2
10mV/div
AC-COUPLED
V
LX2
5V/div
0V
V
LX1
5V/div
0V
V
OUT1
10mV/div
AC-COUPLED
200ns/div
400μs/div
100ms/div
EXTERNALLY SYNCHRONIZED
SWITCHING WAVEFORM
MAX8529 toc10
CKO OUTPUT WAVEFORM
5V
V
SYNC
0V
5V
V
CKO
0V
V
LX1
5V/div
0V
V
OUT1
10mV/div
AC-COUPLED
MAX8529 toc11
CKO OUTPUT WAVEFORM
MAX8529 toc12
SYNC = GND
5V
V
CK0
0V
V
LX1
5V/div
0V
V
OUT1
10mV/div
AC-COUPLED
200ns/div
200ns/div
SYNC = V
L
5V
V
CK0
0V
V
LX1
5V/div
0V
V
OUT1
10mV/div
AC-COUPLED
200ns/div
SHORT-CIRCUIT CURRENT FOLDBACK
AND RECOVERY
MAX8529 toc13
OUTPUT2 NOISE SPECTRUM
MAX8529 toc14
V
OUT1
50mV/div
AC-COUPLED
SHORT
V
OUT2
V
OUT2
1V/div
0V
I
OUT2
2A/div
0A
0
250
750
500
FREQUENCY (kHz)
1000
1250
400nV/√Hz
40nV/√Hz
4nV/√Hz
200μs/div
_______________________________________________________________________________________
5
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