19-3017; Rev 1; 5/05
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
General Description
The MAX8553 is a 4.5V to 28V input-voltage, synchro-
nous step-down controller that provides a complete
power-management solution for DDR memory. The
MAX8553 generates 1/2 V
REFIN
voltage for VTT and
VTTR. The VTT and VTTR tracking voltages are main-
tained within 1% of 1/2 V
REFIN
. The MAX8554 is a 4.5V to
28V input voltage, nontracking step-down controller with
a low 0.6V feedback threshold voltage. The MAX8553/
MAX8554 use Maxim’s proprietary Quick-PWM™ archi-
tecture for fast transient response and operate with
selectable pseudo-fixed frequencies. Both controllers
can operate without an external bias supply.
The controllers operate in synchronous-rectification mode
to ensure balanced current sourcing and sinking capabili-
ty of up to 25A. The MAX8553/MAX8554 also provide up
to 95% efficiency, making them ideal for server and point-
of-load applications. Additionally, a low 5µA shutdown
current allows for longer battery life in notebook applica-
tions. Lossless current monitoring is achieved by monitor-
ing the low-side MOSFET’s drain-to-source voltage. The
MAX8553/MAX8554 have an adjustable foldback current
limit to withstand a continuous output overload and short
circuit. Digital soft-start provides control of inrush current
during power-up. Overvoltage protection shuts the con-
verter down and discharges the output capacitor. The
MAX8553/MAX8554 come in space-saving 16-pin QSOP
packages.
♦
Up to 25A Output-Current Capability
♦
Quick-PWM Control for Fast Loop Response
♦
Up to 95% Efficiency
♦
4.5V to 28V Input Voltage Range
♦
No External Bias Supply Required
♦
0 to 3.6V Input REFIN Range (MAX8553)
♦
Automatically Sets VTT and VTTR to within
±1%
of 1/2 V
REFIN
- (MAX8553)
♦
Low 0.6V Feedback Threshold (MAX8554)
♦
200kHz/300kHz/400kHz/550kHz Selectable
Switching Frequencies
♦
Adjustable Foldback Current Limit
♦
Overvoltage Protection
♦
Digital Soft-Start
Features
MAX8553/MAX8554
Typical Operating Circuit
VIN
+5V
EN/HSD
DH
Applications
Wide-Input Power Supplies
Servers and Storage Applications
ASIC and CPU Core Voltages
Notebook and LCD-PC Power Supplies
DDR I and DDR II Memory Power Supplies
AGTL Bus Termination Supplies
POK
POK
REFIN
MAX8553
VL
REFIN
V+
BST
VOUT
V+
LX
REF
DL
Ordering Information
PART
MAX8553EEE
MAX8554EEE
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
16 QSOP
ILIM
FSEL
GND
PGND
VTT
VTTR
VTTR
Pin Configurations appear at end of data sheet.
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
MAX8553/MAX8554
ABSOLUTE MAXIMUM RATINGS
V+, EN/HSD, EN, HSD to GND...............................-0.3V to +30V
PGND to GND .......................................................-0.3V to +0.3V
VTT, REFIN, POK, OUT, FB, VL to GND...................-0.3V to +6V
REF, VTTR, DL, ILIM, FSEL to GND ............-0.3V to (V
VL
+ 0.3V)
LX to PGND ...............................................................-2V to +30V
BST to GND ............................................................-0.3V to +36V
DH to LX ...................................................................-0.3V to +6V
LX to BST..................................................................-6V to +0.3V
REF Short Circuit to GND ...........................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derated 8.3mW/°C above +70°C) ........667mW
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
V+
= V
HSD
= +12V, V
EN/HSD
= V
REFIN
= +2.5V, V
EN
= +5V, C
VL
= 4.7µF, C
VTTR
= 1µF, C
REF
= 0.22µF, V
FSEL
= 0V, ILIM = VL,
PGND = LX = GND, BST = VL,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise specified.)
PARAMETER
V+ Input Voltage Range
V+ Input Voltage Range
EN/HSD Input Voltage Range
EN Input Voltage Range
EN Input Current
HSD Input Voltage Range
HSD Input Current
REFIN Input Voltage Range
V+ Supply Current (MAX8553)
V+ Supply Current (MAX8554)
REFIN Supply Current
EN/HSD Supply Current
VL Supply Current
V+ Shutdown Supply Current
REFIN Shutdown Supply Current
VL Shutdown Supply Current
VL Undervoltage-Lockout Threshold
VTT
VTT Input Bias Current
VTT Feedback Voltage Range
VTT Feedback Voltage Accuracy
FB Input Bias Current
V
REFIN
= V
EN/HSD
= +1.8V
V
REFIN
= V
EN/HSD
= +3.6V
MAX8554, V
FB
= +600mV
V
VTT
= +1.25V
-0.15
0
49.5
49.5
-0.15
50
50
0
1.8
50.5
50.5
0
µA
V
% V
REFIN
µA
V
VL
= V
V+
= 5.5V, V
VTT
= +1.35V
EN/HSD = GND
EN/HSD = GND
V
VL
= V
V+
= +5.5V, V
EN/HSD
= 0V
Rising edge, typical hysteresis = 40mV
4.05
5
4.25
V
VTT
= +1.35V
V
FB
= 630mV
0
0.8
0.62
125
5
0.8
3
MAX8554 enabled
1.5
20
VL connected to V+
MAX8553 enabled
MAX8554 enabled
CONDITIONS
VL not connected to V+
MIN
6
4.5
1.5
1.5
2
TYP
MAX
28
5.5
28.0
28.0
3
28.0
40
3.6
1.2
0.90
250
10
1.2
5
1
12
4.40
UNITS
V
V
V
V
µA
V
µA
V
mA
mA
µA
µA
mA
µA
µA
µA
V
2
_______________________________________________________________________________________
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
ELECTRICAL CHARACTERISTICS (continued)
(V
V+
= V
HSD
= +12V, V
EN/HSD
= V
REFIN
= +2.5V, V
EN
= +5V, C
VL
= 4.7µF, C
VTTR
= 1µF, C
REF
= 0.22µF, V
FSEL
= 0V, ILIM = VL,
PGND = LX = GND, BST = VL,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise specified.)
PARAMETER
FB Regulation Voltage
Output Adjust Range
VTT Line Regulation
FB Line Regulation
VTT Load Regulation
FB Load Regulation
REFERENCE
Reference Output Voltage
Reference Load Regulation
Reference UVLO
VTTR
VTTR Output Voltage Range
I
VTTR
= -5mA to +5mA
VTTR Output Accuracy
Thermal Shutdown
SOFT-START
ILIM Ramp Period
Output Predischarge Period
OSCILLATOR
FSEL = VL
Oscillator Frequency
FSEL = unconnected
FSEL = REF
FSEL = GND
FSEL = VL
On-Time
MAX8553, V
VTT
= +1.25V
(Note 2)
FSEL unconnected
FSEL = REF
FSEL = GND
FSEL = VL
On-Time
MAX8554, V
OUT
= +2.5V
(Note 2)
(Note 2)
FSEL unconnected
FSEL = REF
FSEL = GND
Off-Time
2.18
1.45
1.09
0.82
0.89
0.61
0.43
0.33
200
300
400
550
2.5
1.67
1.25
0.91
1.02
0.71
0.49
0.37
350
2.83
1.89
1.41
1.00
1.16
0.80
0.56
0.41
400
ns
µs
µs
kHz
Ramps the ILIM trip threshold from 20% to 100% in
20% increments
Rising edge of EN/HSD to the start of internal digital
soft-start
0.8
0.8
1.7
1.7
3.0
3.0
ms
ms
I
VTTR
= -25mA to +25mA, V
REFIN
= +1.8V
I
VTTR
= -25mA to +25mA, V
REFIN
= +3.6V
Rising temperature, typical hysteresis = 15°C
0
49.5
49
49.5
50
50
50
+160
1.8
50.5
51
50.5
°C
V
% V
REFIN
V
V+
= V
VL
= +4.5 to +5.5V, I
REF
= 0
V
V+
= V
VL
= +5V, I
REF
= 0 to 50µA
V
V+
= V
VL
= +5V, reference rising, hysteresis = 27mV
1.5
1.6
1.97
2.00
2.03
10
1.7
V
mV
V
MAX8554 (Note 1)
V
EN/HSD
±10%, V
VTT
= +1.25V, I
OUT
= 0A
MAX8554, V
HSD
±10%, V
OUT
= +2.5V,
I
OUT
= 0A, FSEL unconnected
0 < I
OUT
< +7A, V
VTT
= +1.25V
MAX8554, 0 < I
OUT
< +7A, V
OUT
= +2.5V,
FSEL unconnected
CONDITIONS
MAX8554, V
OUT
= +2.5V, FSEL unconnected
MIN
0.598
0.6
±0.325
±0.325
0.2
0.2
TYP
0.607
MAX
0.616
3.5
UNITS
V
V
%
%
%
%
MAX8553/MAX8554
_______________________________________________________________________________________
3
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
MAX8553/MAX8554
ELECTRICAL CHARACTERISTICS (continued)
(V
V+
= V
HSD
= +12V, V
EN/HSD
= V
REFIN
= +2.5V, V
EN
= +5V, C
VL
= 4.7µF, C
VTTR
= 1µF, C
REF
= 0.22µF, V
FSEL
= 0V, ILIM = VL,
PGND = LX = GND, BST = VL,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise specified.)
PARAMETER
CURRENT LIMIT
LX to PGND, ILIM = VL
Current-Limit Threshold (Positive
Direction)
Current-Limit Threshold (Negative
Direction)
ILIM Input Current
FAULT DETECTION
MAX8553 (V
REFIN
> +1V)
Overvoltage Threshold
VL REGULATOR
Output Voltage
Line Regulation
RMS Output Current
Bypass Capacitor
DRIVER
DH Gate-Driver On-Resistance
DL Gate-Driver On-Resistance
(Source)
DL Gate-Driver On-Resistance
(Sink)
Dead Time
FSEL LOGIC
Logic Input Current
Logic Low (GND)
Logic REF Level
Logic Float Level
Logic VL Level
EN/HSD OR EN LOGIC
EN/HSD or EN Shutdown Current
Logic High
Logic Low
Max I
EN/HSD
for V
EN/HSD
< +0.8V or V
EN
< +0.8V
V
VL
= V
V+
= +4.5 to +5.5V, 100mV hysteresis
V
VL
= V
V+
= +4.5 to +5.5V
0.5
1.5
0.8
3.0
µA
V
V
FSEL = REF
FSEL unconnected
FSEL = VL
1.65
3.15
V
VL
- 0.4
-3
+3
0.5
2.35
3.85
µA
V
V
V
V
V
BST
- V
LX
= +5V
DL high state
DL low state
DL rising
DL falling
1.4
1.6
0.75
32
30
2.5
3.0
1.25
Ω
Ω
Ω
ns
ESR < 100mΩ
2.2
+6V < V
V+
<+28V, 1mA < I
VL
< 35mA
+6V < V
V+
< +28V, I
VL
= 10mA
4.80
5.0
0.2
35
5.33
V
%
mA
µF
MAX8553 (V
REFIN
≤
+1V)
MAX8554
57
0.576
0.696
60
0.600
0.720
63
0.624
0.744
% V
REFIN
V
LX to PGND, R
ILIM
= 100kΩ
LX to PGND, R
ILIM
= 400kΩ
LX to PGND, ILIM = VL, with respect to positive
current-limit threshold
80
35
160
-130
100
50
200
-110
5
115
65
230
-90
%
µA
mV
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
ELECTRICAL CHARACTERISTICS (continued)
(V
V+
= V
HSD
= +12V, V
EN/HSD
= V
REFIN
= +2.5V, V
EN
= +5V, C
VL
= 4.7µF, C
VTTR
= 1µF, C
REF
= 0.22µF, V
FSEL
= 0V, ILIM = VL,
PGND = LX = GND, BST = VL,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise specified.)
PARAMETER
POWER-OK OUTPUT
Upper VTT and VTTR Threshold
Lower VTT and VTTR Threshold
Upper Threshold
Lower Threshold
POK Output Low Level
POK Output High Leakage
MAX8553
MAX8553
MAX8554
MAX8554
I
SINK
= 2mA
V
POK
= +5V
55
43
0.646
0.504
56
44
0.672
0.528
57
45
0.698
0.552
0.4
5
% V
REFIN
% V
REFIN
V
V
V
µA
CONDITIONS
MIN
TYP
MAX
UNITS
MAX8553/MAX8554
ELECTRICAL CHARACTERISTICS
(V
V+
= V
HSD
= +12V, V
EN/HSD
= V
REFIN
= +2.5V, V
EN
= +5V, C
VL
= 4.7µF, C
VTTR
= 1µF, C
REF
= 0.22µF, V
FSEL
= 0, ILIM = VL, PGND
= LX = POK = GND, BST = VL,
T
A
= -40°C to +85°C,
unless otherwise specified.) (Note 3)
PARAMETER
V+ Input Voltage Range
V+ Input Voltage Range
EN/HSD Input Voltage Range
EN Input Voltage Range
EN Input Current
HSD Input Voltage Range
HSD Input Current
REFIN Input Voltage Range
V+ Supply Current (MAX8553)
V+ Supply Current (MAX8554)
REFIN Supply Current
EN/HSD Supply Current
VL Supply Current
V+ Shutdown Supply Current
REFIN Shutdown Supply Current
VL Shutdown Supply Current
VL Undervoltage-Lockout Threshold
VTT
VTT Input Bias Current
VTT Feedback Voltage Range
VTT Feedback Voltage Accuracy
FB Input Bias Current
FB Regulation Voltage
Output Adjust Range
V
REFIN
= V
EN/HSD
= +1.8V
V
REFIN
= V
EN/HSD
= +3.6V
MAX8554, V
FB
= +600mV
MAX8554, V
OUT
= +2.5V, FSEL unconnected
MAX8554 (Note 1)
V
VTT
= +1.25V
-0.2
0
49.5
49.5
-0.2
0.598
0.6
0
1.8
50.5
50.5
0
0.616
3.5
µA
V
% V
REFIN
µA
V
V
V
VL
= V
V+
= 5.5V, V
VTT
= +1.35V
EN/HSD = GND
EN/HSD = GND
V
VL
= V
V+
= +5.5V, V
EN/HSD
= 0V
Rising edge, typical hysteresis = 40mV
4.05
V
VTT
= +1.35V
V
FB
= 630mV
0
MAX8554 enabled
1.5
VL connected to V+
MAX8553 enabled
MAX8554 enabled
CONDITIONS
VL not connected to V+
MIN
6
4.5
1.5
1.5
MAX
28
5.5
28.0
28.0
3
28.0
40
3.6
1.2
0.90
250
10
1.2
5
1
12
4.40
UNITS
V
V
V
V
µA
V
µA
V
mA
mA
µA
µA
mA
µA
µA
µA
V
_______________________________________________________________________________________
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