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PDF MAX8554 Data sheet ( Hoja de datos )
| Número de pieza | MAX8554 | |
| Descripción | 4.5V to 28V Input / Synchronous PWM Buck Controllers for DDR Termination and Point-of-Load Applications | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-3017; Rev 0; 10/03
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 VREFIN voltage for VTT and
VTTR. The VTT and VTTR tracking voltages are main-
tained within 1% of 1/2 VREFIN. 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.
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
PART
MAX8553EEE
MAX8554EEE
Ordering Information
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
16 QSOP
Features
o Up to 25A Output-Current Capability
o Quick-PWM Control for Fast Loop Response
o Up to 95% Efficiency
o 4.5V to 28V Input Voltage Range
o No External Bias Supply Required
o 0 to 3.6V Input REFIN Range (MAX8553)
o Automatically Sets VTT and VTTR to within ±1%
of 1/2 VREFIN- (MAX8553)
o Low 0.6V Feedback Threshold (MAX8554)
o 200kHz/300kHz/400kHz/550kHz Selectable
Switching Frequencies
o Adjustable Foldback Current Limit
o Overvoltage Protection
o Digital Soft-Start
Typical Operating Circuit
VIN
+5V
POK
REFIN
V+
EN/HSD
DH
MAX8553
POK VL
REFIN
BST
V+ LX
VOUT
REF DL
ILIM PGND
FSEL VTT
GND 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.
1 page  
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
ELECTRICAL CHARACTERISTICS (continued)
(VV+ = VHSD = +12V, VEN/HSD = VREFIN = +2.5V, VEN = +5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0V, ILIM = VL,
PGND = LX = GND, BST = VL, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise specified.)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
POWER-OK OUTPUT
Upper VTT and VTTR Threshold
Lower VTT and VTTR Threshold
Upper Threshold
MAX8553
MAX8553
MAX8554
55
43
0.646
56
44
0.672
57
45
0.698
% VREFIN
% VREFIN
V
Lower Threshold
MAX8554
0.504 0.528 0.552
V
POK Output Low Level
POK Output High Leakage
ISINK = 2mA
VPOK = +5V
0.4 V
5 µA
ELECTRICAL CHARACTERISTICS
(VV+ = VHSD = +12V, VEN/HSD = VREFIN = +2.5V, VEN = +5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0, ILIM = VL, PGND
= LX = POK = GND, BST = VL, TA = -40°C to +85°C, unless otherwise specified.) (Note 3)
PARAMETER
CONDITIONS
MIN MAX UNITS
V+ Input Voltage Range
VL not connected to V+
6 28 V
V+ Input Voltage Range
VL connected to V+
4.5 5.5 V
EN/HSD Input Voltage Range
MAX8553 enabled
1.5 28.0 V
EN Input Voltage Range
MAX8554 enabled
1.5 28.0 V
EN Input Current
3 µA
HSD Input Voltage Range
MAX8554 enabled
1.5 28.0 V
HSD Input Current
40 µA
REFIN Input Voltage Range
0 3.6 V
V+ Supply Current (MAX8553)
V+ Supply Current (MAX8554)
REFIN Supply Current
VVTT = +1.35V
VFB = 630mV
1.2
0.90
250
mA
mA
µA
EN/HSD Supply Current
10 µA
VL Supply Current
V+ Shutdown Supply Current
VVL = VV+ = 5.5V, VVTT = +1.35V
EN/HSD = GND
1.2 mA
5 µA
REFIN Shutdown Supply Current
EN/HSD = GND
1 µA
VL Shutdown Supply Current
VVL = VV+ = +5.5V, VEN/HSD = 0V
VL Undervoltage-Lockout Threshold Rising edge, typical hysteresis = 40mV
4.05
12 µA
4.40 V
VTT
VTT Input Bias Current
VTT Feedback Voltage Range
VVTT = +1.25V
-0.2 0 µA
0 1.8 V
VTT Feedback Voltage Accuracy
FB Input Bias Current
FB Regulation Voltage
Output Adjust Range
VREFIN = VEN/HSD = +1.8V
VREFIN = VEN/HSD = +3.6V
MAX8554, VFB = +600mV
MAX8554, VOUT = +2.5V, FSEL unconnected
MAX8554 (Note 1)
49.5
49.5
-0.2
0.598
0.6
50.5
50.5
0
0.616
3.5
% VREFIN
µA
V
V
_______________________________________________________________________________________ 5
5 Page 
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
Pin Description
PIN MAX8553 MAX8554
FUNCTION
EN/HSD
1
Enable/High-Side Drain. Connect to the high-side N-channel MOSFET drain through a 5.1kΩ
— resistor for normal operation. Connect to GND for low-power shutdown (Figure 2). If the enable
function is not used, connect EN/HSD directly to the high-side N-channel MOSFET drain.
— HSD High-Side Drain. Connect to the high-side N-channel MOSFET drain for normal operation.
REFIN
2
—
— Reference Input. An applied voltage at REFIN sets VVTT and VVTTR to 1/2 VREFIN. REFIN voltage
range is from 0 to +3.6V.
EN
Enable. Drive EN high to enable the output. Drive EN low to shut down the IC. If the enable
function is not used, connect EN to V+.
3 POK
POK
Power-OK Output. POK is an open-drain output and is logic high when both VTT and VTTR are
within 12% of regulation. POK is pulled low in shutdown.
VTT — VTT Feedback Input. Connect to VTT output.
4
—
FB
Output Feedback. Connect to the center of a resistor-divider between the output and ground to
set the output voltage. FB threshold is 0.6V.
5 ILIM
ILIM Current-Limit Threshold Adjustment. Connect a resistor from ILIM to GND to set the current-limit
threshold, or connect ILIM to VL for the default setting. See the Setting the Current Limit section.
6 FSEL FSEL Frequency Select. Selects the switching frequency. See Tables 1 and 2 for configuration of
FSEL.
7 REF
REF Reference. Connect a 0.22µF or greater capacitor from REF to GND.
8 GND GND Ground
VTTR
9
—
—
OUT
VTTR Reference Output. Connect a 1µF or greater capacitor from VTTR to GND. VTTR is
capable of sourcing and sinking up to 25mA.
Output Voltage. Connect directly to the output. OUT senses the output voltage to determine the
on-time for the high-side switching MOSFET.
10 V+
V+
Input Supply Voltage. Supply input for the VL regulator. Bypass with a 0.22µF or greater
capacitor.
11 VL
VL
Internal Regulator Output. Connect a 2.2µF or greater capacitor from VL to GND. VL can be
connected to V+ if the operating range is from +4.5V to +5.5V.
12 DL
DL
Low-Side MOSFET Gate Drive. Connect to the gate of the low-side N-channel MOSFET. DL is
low in shutdown or in undervoltage lockout.
13 PGND PGND Power Ground
14 BST
BST Bootstrapped Supply. Drives high-side N-channel MOSFET. Connect a 0.1µF or greater
capacitor from BST to LX.
15 DH
16 LX
DH High-Side MOSFET Gate Drive. Connect to the high-side N-channel MOSFET gate. DH is low in
shutdown or in undervoltage lockout.
LX Inductor Switching Node
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet MAX8554.PDF ] | |
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