19-0588; Rev 3; 6/11
KIT
ATION
EVALU
E
BL
AVAILA
12V, 8A 1.2MHz
Step-Down Regulator
General Description
Features
o
o
o
o
o
o
o
o
Internal 26mΩ R
DS(ON)
MOSFETs
Guaranteed 8A Output Current
Adjustable Overcurrent Protection
1% Output Accuracy Over Temperature
Operates from 4.5V to 14V Supply
Adjustable Output from 0.6V to 0.85 x V
IN
Soft-Start Reduces Inrush Supply Current
250kHz to 1.2MHz Adjustable Switching or SYNC
Input
o
Compatible with Ceramic, Polymer, and
Electrolytic Output Capacitors
o
SYNCOUT Synchronizes 2nd Regulator 180°
Out-of-Phase
o
36-Pin, Lead-Free, 6mm x 6mm TQFN Package
MAX8654
The MAX8654 high-efficiency switching regulator delivers
up to 8A of load current at output voltages from 0.6V to
0.85 x V
IN
. The IC operates from 4.5V to 14V, making it
ideal for on-board point-of-load and postregulation appli-
cations, with total output error less than ±1% over load,
line, and temperature ranges.
The MAX8654 is a fixed-frequency PWM mode regulator
with a switching frequency range of 250kHz to 1.2MHz
set by an external resistor or SYNC input. High-frequency
operation allows for an all-ceramic-capacitor solution. A
SYNCOUT output is provided to synchronize a second
regulator switching 180° out-of-phase with the first to
reduce the input ripple current and consequently reduce
the required input capacitance. The high operating fre-
quency minimizes the size of external components.
The on-board low R
DS(ON)
dual-nMOS design keeps
the board cooler at heavy loads while minimizing the
critical inductances, making the layout a much simpler
task with respect to the discrete solutions.
The MAX8654 comes with a high-bandwidth (20MHz)
voltage-error amplifier. The voltage-mode control archi-
tecture and the op-amp voltage-error amplifier permit a
type 3 compensation scheme to be utilized to achieve
maximum loop bandwidth, up to 20% of the switching
frequency. High loop bandwidth achieves fast transient
response resulting in less output capacitance required.
The MAX8654 offers programmable soft-start to accom-
modate different types of output capacitors and reduce
input inrush current. The MAX8654 is available in a 36-
lead TQFN package.
Ordering Information
PART
MAX8654ETX+
TEMP RANGE
-40°C to +85°C
PIN-
PACKAGE
36 TQFN-EP*
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
Typical Operating Circuit
INPUT
4.5V TO 14V
IN
VP
VL
VL
VDL
LX
BST
OUTPUT
UP TO 8A
Applications
POL Power Supplies
Servers
DDR Memory
RAID Power Supplies
Network Power Supplies
Graphic Cards
PGND
MAX8654
FREQ
ILIM
REFIN
SS
FB
COMP
SYNC
VL
SYNCOUT
IN
EN
GND
PWRGD
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.
12V, 8A 1.2MHz
Step-Down Regulator
MAX8654
ABSOLUTE MAXIMUM RATINGS
SYNC, VL, PWRGD to GND...................................-0.3V to +4.5V
SYNCOUT, COMP, SS, FB,
REFIN, ILIM, FREQ to GND .....................-0.3V to (V
VL
+ 0.3V)
VDL to PGND............................................................-0.3V to +6V
VP, IN, EN to GND..................................................-0.3V to +16V
LX Current (Note 1: -12A to +12A)
BST to LX .………………………………………………-0.3V to +6V
BST to GND ……………………………………..-0.3V to (V
IN
+ 6V)
EN to VP and IN………………………………-0.3V to (V
IN
+ 0.3V)
PGND to GND .......................................................-0.3V to +0.3V
Continuous Power Dissipation (T
A
= +70°C)
36-Pin TQFN (derate 35.7mW/°C above +70°C) .........2857.1mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......………………………………….+150°C
Storage Temperature Range .............................-65°C to +150°C
Thermal Resistance Junction to Exposed Pad (EP)...........3°C/W
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
Note 1:
LX has internal clamp diodes to PGND and IN. Applications that forward bias these diodes should take care not to exceed
the IC’s package power-dissipation limits.
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
= V
EN
= V
VP
= 12V, V
VDL
= 5V, V
VL
= 3.3V, V
SYNC
= 0V, V
FB
= 0.5V,
T
A
= -40°C to +85°C,
typical values are at T
A
= +25°C,
unless otherwise noted.)
PARAMETER
IN/VP
IN and VP Voltage Range
VDL Voltage Range
VL Output Voltage
VDL Output Voltage
IN + VP Supply Current
VL Supply Current
VDL Supply Current
IN + VP Shutdown Current
VL Undervoltage Lockout
Threshold
VDL and IN Undervoltage
Lockout Threshold
BST
BST Shutdown Supply Current
PWM COMPARATOR
PWM Comparator Propagation
Delay
COMP
COMP Clamp Voltage, High
COMP Slew Rate
COMP Shutdown Resistance
From COMP to GND, V
EN
= 0V
1.8
7
7
V
V/µs
Ω
5mV overdrive
16
ns
V
EN
= 0V, V
IN
= V
VP
= V
BST
= V
VDL
= 5V
10
µA
VP = VDL
I
VL
= 5mA
I
VDL
= 50mA
Not switching, no load
f
S
= 500kHz, no load,
L = 1.5µH
V
IN
= 12V
V
IN
= 4.5V
4.5
4.5
3.3
5
2.7
45
28
1.6
25
10
3
2.8
3.8
2.9
4.4
20
3.1
mA
mA
µA
V
V
mA
14
5.5
V
V
V
V
CONDITIONS
MIN
TYP
MAX
UNITS
f
S
= 500kHz, V
VL
= 3.8V from separate supply
f
S
= 500kHz, V
VDL
= 5.5V from separate supply
V
P
= V
IN
= 13.2V, V
EN
= V
VDL
= V
VL
= unconnected
LX starts/stops switching,
2µs rising/falling edge deglitch
LX starts/stops switching,
3µs rising/falling edge deglitch
V
VL
rising
V
VL
falling
V
IN
rising
V
IN
falling
2
_______________________________________________________________________________________
12V, 8A 1.2MHz
Step-Down Regulator
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
EN
= V
VP
= 12V, V
VDL
= 5V, V
VL
= 3.3V, V
SYNC
= 0V, V
FB
= 0.5V,
T
A
= -40°C to +85°C,
typical values are at T
A
= +25°C,
unless otherwise noted.)
PARAMETER
ERROR AMPLIFIER
FB Regulation Voltage
Open-Loop Voltage Gain
Error-Amplifier Unity-Gain
Bandwidth
Error-Amplifier Common-Mode
Input Range
Error-Amplifier Maximum Output
Current
FB Input Bias Current
REFIN
REFIN Input Bias Current
REFIN Common-Mode Range
LX (All Pins Combined)
LX On-Resistance, High Side
LX On-Resistance, Low Side
LX Current-Limit Threshold
R
ILIM
Range
LX Leakage Current
LX Switching Frequency
R
FREQ
Range
LX Minimum On-Time
Maximum RMS LX Output Current
EN/SS
EN Input Logic-Low Threshold
EN Input Logic-High Threshold
EN Input Current
SS Current
REFIN Discharge Resistance
Current-Limit Startup Blanking
Restart Time
V
EN
= 0V
V
EN
= 14V
V
SS
= 0.45V
-10
1.2
-1
7
-8
500
110
900
-6
0.6
V
V
µA
µA
Ω
Clock
cycles
Clock
cycles
(Note 2)
10.5
V
EN
= 0V
V
LX
= 14V = V
IN
V
LX
= 0V, V
IN
= 14V
R
FREQ
= 50kΩ
R
FREQ
= 100kΩ
-50
0.85
0.45
50
80
1
0.5
1.1
0.55
200
I
LX
= -180mA
I
LX
= 180mA
R
ILIM
= 100kΩ
Sourcing
Sinking
7
7
40
V
BST
- V
LX
= 5V
36
25
8
8
64
40
10
10
200
+50
mΩ
mΩ
A
kΩ
µA
MHz
kΩ
ns
A
V
REFIN
= 0.6V
0
-60
1.5
nA
V
V
COMP
= 1V
V
FB
= 0.6V
VP = V
IN
= 4.5V to 14V
1kΩ from COMP to GND
Parallel 10kΩ, 160pF from COMP to GND
0
1
-35
0.594
0.6
95
20
1.5
0.606
V
dB
MHz
V
mA
nA
CONDITIONS
MIN
TYP
MAX
UNITS
MAX8654
_______________________________________________________________________________________
3
12V, 8A 1.2MHz
Step-Down Regulator
MAX8654
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
EN
= V
VP
= 12V, V
VDL
= 5V, V
VL
= 3.3V, V
SYNC
= 0V, V
FB
= 0.5V,
T
A
= -40°C to +85°C,
typical values are at T
A
= +25°C,
unless otherwise noted.)
PARAMETER
SYNC
SYNC Capture Range
SYNC Pulse Width
SYNC Input Threshold
SYNC Input Current
SYNCOUT
SYNCOUT Frequency Range
SYNCOUT Phase Shift from
SYNCIN or Internal Oscillator
SYNCOUT Output Voltage
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
POWER-GOOD
PWRGD Threshold Voltage
PWRGD Falling Edge Deglitch
PWRGD Output Voltage Low
PWRGD Leakage Current
I
PWRGD
= 4mA
V
PWRGD
= 5.5V, V
FB
= 0.9V
V
FB
falling, 30mV hysteresis, V
REFIN
> 540mV
90
48
0.03
0.01
0.06
1
% of
REFIN
Clock
cycles
V
µA
When LX stops switching
+165
20
°C
°C
Frequency = 1MHz
I
SYNCOUT
=
±1mA
V
OH
V
OL
0.25
170
V
VL
- 0.4
0.2
180
1.2
190
MHz
Degrees
V
t
LO
t
HI
V
IL
V
IH
V
SYNC
= 0V or 3.6V
I
IL
I
IH
10
7
0.25
100
100
0.4
1.6
1.20
MHz
ns
V
nA
µA
CONDITIONS
MIN
TYP
MAX
UNITS
Note 2:
All devices are production tested at T
A
= +25°C. Limits over the operating range are guaranteed by design.
4
_______________________________________________________________________________________
12V, 8A 1.2MHz
Step-Down Regulator
MAX8654
Typical Operating Characteristics
(Typical values are: V
IN
= V
VP
= 12V, V
OUT
= 3.3V, R
FREQ
= 100kΩ, and T
A
= +25°C, circuit of Figure 1.)
EFFICIENCY vs. LOAD CURRENT
MAX8654 toc01
EFFICIENCY vs. LOAD CURRENT
MAX8654 toc02
EFFICIENCY vs. LOAD CURRENT
90
80
EFFICIENCY (%)
70
60
50
40
30
20
V
OUT
= 3.3V
V
OUT
= 1.8V
V
OUT
= 5V
MAX8654 toc03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
V
IN
= 12V, V
VDL
= V
VP
= 5V, f
S
= 500kHz
1
OUTPUT CURRENT (A)
V
OUT
= 1.8V
V
OUT
= 5V
V
OUT
= 3.3V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
V
IN
= V
VP
= 5V, f
S
= 500kHz
0.1
1
OUTPUT CURRENT (A)
V
OUT
= 1.8V
V
OUT
= 3.3V
100
10
0
10
V
IN
= V
VP
= 12V, f
S
= 500kHz
0.1
1
OUTPUT CURRENT (A)
10
10
REFERENCE VOLTAGE vs. TEMPERATURE
MAX8654 toc04
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
MAX8654 toc05
SWITCHING FREQUENCY vs. R
FREQ
MAX8654 toc06
0.610
1200
1000
800
600
400
200
1400
1200
1000
800
600
400
200
0
SWITCHING FREQUENCY (kHz)
0.605
0.600
0.595
0.590
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
0
5
7
9
11
13
15
INPUT VOLTAGE (V)
SWITCHING FREQUENCY (kHz)
REFERENCE VOLTAGE (V)
0
50
100
150
200
250
R
FREQ
(kΩ)
LOAD REGULATION
MAX8654 toc07
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX8654 toc08
CURRENT LIMIT vs. OUTPUT VOLTAGE
8.8
8.6
CURRENT LIMIT (A)
8.4
8.2
8.0
7.8
7.6
7.4
7.2
7.0
MAX8654 toc09
0
V
OUT
= 3.3V
OUTPUT VOLTAGE CHANGE (%)
-0.05
-0.10
-0.15
V
OUT
= 1.8V
-0.20
-0.25
-0.30
-0.35
0
1
2
3
4
5
6
7
8
LOAD CURRENT (A)
10
SHUTDOWN SUPPLY CURRENT (µA)
9
8
7
6
5
4
3
2
1
0
0
2
4
6
8
10
12
9.0
14
1.5
.2.0
2.5
3.0
3.5
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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