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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1858A Datasheet

Dual 180 Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR

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19-2966; Rev 0; 10/03
EVAALVUAAILTAIOBNLEKIT
Dual 180° Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
General Description
The MAX1858A/MAX1875A/MAX1876A dual, synchro-
nized, step-down controllers generate two outputs from
input supplies ranging from 4.5V to 23V. Each output is
adjustable from sub-1V to 18V and supports loads of 10A
or higher. Input voltage ripple and total RMS input ripple
current are reduced by synchronized 180° out-of-phase
operation.
The switching frequency is adjustable from 100kHz to
600kHz with an external resistor. Alternatively, the con-
troller can be synchronized to an external clock gener-
ated by another MAX1858A/MAX1875A/MAX1876A or a
system clock. One MAX1858A/MAX1875A/MAX1876A
can be set to generate an in-phase, or 90° out-of-
phase, clock signal for synchronization with additional
controllers. This allows two controllers to operate either
as an interleaved two- or four-phase system with each
output shifted by 90°. The MAX1858A/MAX1875A/
MAX1876A feature soft-start. The MAX1858A also fea-
tures first-on/last-off power sequencing and soft-stop.
The MAX1858A/MAX1875A/MAX1876A eliminate the
need for current-sense resistors by utilizing the low-side
MOSFET’s on-resistance as a current-sense element.
This protects the DC-DC components from damage dur-
ing output-overload conditions or output short-circuit
faults without requiring a current-sense resistor.
Adjustable foldback current limit reduces power dissipa-
tion during short-circuit conditions. The MAX1858A/
MAX1876A include a power-on reset (POR) output to sig-
nal the system when both outputs reach regulation.
The MAX1858A/MAX1875A/MAX1876A ensure that the
output voltage does not swing negative when the input
power is removed or when EN is driven low. The
MAX1875A/MAX1876A also allow prebias startup with-
out discharging the output.
The MAX1858A/MAX1875A/MAX1876A are available in a
24-pin QSOP package. Use the MAX1875 evaluation kit
or the MAX1858 evaluation kit to evaluate the
MAX1858A/MAX1875A/MAX1876A.
Applications
Network Power Supplies
Telecom Power Supplies
DSP, ASIC, and FPGA Power Supplies
Set-Top Boxes
Broadband Routers
Servers
Desknote Computers
Features
o 4.5V to 23V Input Supply Range
o 0 to 18V Output Voltage Range (Up to 10A)
o Adjustable Lossless Foldback Current Limit
o Adjustable 100kHz to 600kHz Switching
Frequency
o Optional Synchronization
o Clock Output for Master/Slave Synchronization
o 4 x 90° Out-of-Phase Step-Down Converters
(Using Two Controllers, Figure 7)
o Prebias Startup (MAX1875A/MAX1876A)
o Power Sequencing (MAX1858A)
o RST Output with 140ms Minimum Delay
(MAX1858A/MAX1876A)
o Fixed-Frequency Pulse-Width Modulation (PWM)
Operation
Ordering Information
PART
MAX1858AEEG
MAX1875AEEG
MAX1876AEEG
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 QSOP
24 QSOP
24 QSOP
Pin Configuration
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
MAX1858A
MAX1875A
MAX1876A
QSOP
24 EN
23 DH2
22 LX2
21 BST2
20 DL2
19 VL
18 PGND
17 DL1
16 BST1
15 LX1
14 DH1
13 RST (N.C.)
() ARE FOR THE MAX1875A ONLY
________________________________________________________________ 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.


Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1858A Datasheet

Dual 180 Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR

No Preview Available !

Dual 180° Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
ABSOLUTE MAXIMUM RATINGS
V+ to GND ..............................................................-0.3V to +25V
PGND to GND .......................................................-0.3V to +0.3V
VL 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 (VBST1 + 0.3V)
DH2 to LX2 ..............................................-0.3V to (VBST2 + 0.3V)
DL1, DL2 to PGND........................................-0.3V to (VL + 0.3V)
CKO, REF, OSC, ILIM1, ILIM2,
COMP1, COMP2 to GND ..........................-0.3V to (VL + 0.3V)
FB1, FB2, RST, SYNC, EN to GND...........................-0.3V to +6V
VL to GND Short Circuit .............................................Continuous
REF to GND Short Circuit ...........................................Continuous
Continuous Power Dissipation (TA = +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_ = VL, SYNC = GND, IVL = 0mA, PGND = GND, CREF = 0.22µF, CVL = 4.7µF (ceramic), ROSC = 60k,
compensation components for COMP_ are from Figure 1, TA = -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
VL REGULATOR
Output Voltage
VL Undervoltage Lockout Rising
Trip Level
CONDITIONS
(Note 2)
VL = V+ (Note 2)
VL unloaded, no MOSFETs connected
EN = LX_ = FB_ = 0V
Rising temperature, typical hysteresis = 10°C
ILIM_ = VL
PGND - LX_
RILIM_ = 100k
RILIM_ = 600k
5.5V < V+ < 23V, 1mA < ILOAD < 50mA
MIN TYP MAX UNITS
4.5 23.0
4.5 5.5
3.5 6
0.3 0.6
+160
75 100 125
32 50 62
225 300 375
4.75 5 5.25
4.1 4.2 4.3
V
mA
mA
°C
mV
V
V
VL Undervoltage Lockout
Hysteresis
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
(Note 3)
100 mV
IREF = 0µA
0µA < IREF < 50µA
1.98 2.00 2.02
0 4 10
V
mV
Internal 6-bit DAC for one converter to ramp from 0V to
full scale (Note 4)
1024
64
DC-DC
clocks
Steps
ROSC = 60k
ROSC = 10k
ROSC = 10k
0°C to +85°C
-40°C to +85°C
84 100 115
80 100 120
540 600 660
250 303
kHz
kHz
ns
2 _______________________________________________________________________________________


Part Number MAX1858A
Description Dual 180 Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR
Maker Maxim
Total Page 22 Pages
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