MAX1876AEEG ,Dual 180 Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and PORELECTRICAL CHARACTERISTICS(V+ = 12V, EN = ILIM_ = V , SYNC = GND, I = 0mA, PGND = GND, C = 0.22µF, ..
MAX1876AEEG+ ,Dual 180° Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and PORELECTRICAL CHARACTERISTICS(V+ = 12V, EN = ILIM_ = V , SYNC = GND, I = 0mA, PGND = GND, C = 0.22µF, ..
MAX1876AEEG+T ,Dual 180° Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and PORApplicationsMAX1858AREF 6 19 VLNetwork Power Supplies MAX1875AGND 7 18 PGNDMAX1876ATelecom Power Su ..
MAX1876EEG ,Dual 180 Out-of-Phase PWM Step- Down Controllers with PORELECTRICAL CHARACTERISTICS(V+ = 12V, EN = ILIM_ = V , SYNC = GND, I = 0mA, PGND = GND, C = 0.22µF, ..
MAX1876EEG ,Dual 180 Out-of-Phase PWM Step- Down Controllers with PORFeaturesThe MAX1875/MAX1876 dual, synchronized, step-down Two Independent Output Voltagescontrolle ..
MAX1876EEG+ ,Dual 180° Out-of-Phase PWM Step-Down Controllers with PORMAX1875/MAX187619-2431; Rev 0; 7/02Dual 180° Out-of-Phase PWM Step-Down Controllers with POR
MAX481EEPA+ ,±15kV ESD-Protected, Slew-Rate-Limited, Low-Power, RS-485/RS-422 Transceiversapplications that are not ESD sensitive see the pin-and function-compatible MAX481, MAX483, MAX485, ..
MAX481EEPA+ ,±15kV ESD-Protected, Slew-Rate-Limited, Low-Power, RS-485/RS-422 TransceiversApplicationsMAX481EESA -40°C to +85°C 8 SOIndustrial-Control Local Area Networks MAX483ECPA 0°C to ..
MAX481EESA ,【15kV ESD-Protected, Slew-Rate-Limited, Low-Power, RS-485/RS-422 TransceiversApplicationsMAX481EESA -40°C to +85°C 8 SOLow-Power RS-485 TransceiversOrdering Information continu ..
MAX481EESA ,【15kV ESD-Protected, Slew-Rate-Limited, Low-Power, RS-485/RS-422 Transceiversapplications. For
MAX481EESA+ ,±15kV ESD-Protected, Slew-Rate-Limited, Low-Power, RS-485/RS-422 Transceiversapplications that are not ESD sensitive see the pin-and function-compatible MAX481, MAX483, MAX485, ..
MAX481EESA+T ,±15kV ESD-Protected, Slew-Rate-Limited, Low-Power, RS-485/RS-422 TransceiversELECTRICAL CHARACTERISTICS(V = 5V ±5%, T = T to T , unless otherwise noted.) (Notes 1, 2)CC A MIN M ..
MAX1858AEEG-MAX1876AEEG
Dual 180 Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR
General DescriptionThe 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/MAX1876Aor 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.
ApplicationsNetwork Power Supplies
Telecom Power Supplies
DSP, ASIC, and FPGA Power Supplies
Set-Top Boxes
Broadband Routers
Servers
Desknote Computers
Features4.5V to 23V Input Supply Range0 to 18V Output Voltage Range (Up to 10A)Adjustable Lossless Foldback Current LimitAdjustable 100kHz to 600kHz Switching
FrequencyOptional SynchronizationClock Output for Master/Slave Synchronization4 x 90°Out-of-Phase Step-Down Converters
(Using Two Controllers, Figure 7)Prebias Startup (MAX1875A/MAX1876A)Power Sequencing (MAX1858A)RST
Output with 140ms Minimum Delay
(MAX1858A/MAX1876A)Fixed-Frequency Pulse-Width Modulation (PWM)
Operation
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
Pin Configuration
Ordering Information
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
ABSOLUTE MAXIMUM RATINGSStresses 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.
V+ to GND..............................................................-0.3V to +25V
PGND to GND.......................................................-0.3V to +0.3Vto 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
ELECTRICAL CHARACTERISTICS(V+ = 12V, EN = ILIM_ = VL, SYNC = GND, IVL= 0mA, PGND = GND, CREF= 0.22µF, CVL= 4.7µF (ceramic), ROSC= 60kΩ,
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
ELECTRICAL CHARACTERISTICS (continued)(V+ = 12V, EN = ILIM_ = VL, SYNC = GND, IVL= 0mA, PGND = GND, CREF= 0.22µF, CVL= 4.7µF (ceramic), ROSC= 60kΩ,
Note 2:Operating supply range is guaranteed by VLline regulation test. Connect V+ to VLfor 5V operation.
Note 3:When VLfalls and UVLO is tripped, the device is latched and VLmust be discharged below 2.5V before normal operation
can resume.
Note 4:Guaranteed by design and not production tested.
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
Typical Operating Characteristics(Circuit of Figure 1, VIN= 12V, TA = +25°C, unless otherwise noted.)
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
INPUT POWER REMOVALMAX1858A/75A/76A toc10
5ms/div
VIN
10V/div
VOUT1
1V/div
IOUT1 = 300mA
VOUT2
1V/div
IOUT2 = 300mA
CKO OUTPUT WAVEFORMMAX1858A/75A/76A toc14
400ns/div
VOUT1
10mV/div
AC-COUPLED
VCK0
VLX1
10V
CKO OUTPUT WAVEFORMMAX1858A/75A/76A toc15
400ns/div
VOUT1
10mV/div
VCK0
VLX1
10V
ypical Operating Characteristics (continued)
SHORT-CIRCUIT CURRENT FOLDBACK
AND RECOVERYMAX1858A/75A/76A toc16
4ms/div
IOUT1 = 10A (5A/div)
VOUT1 = 1.8V (1V/div)
VOUT2 = 2.5V (1V/div)
IOUT2 = 10A (5A/div)
RESET TIMEOUT
(MAX1858A/MAX1876A ONLY)MAX1858A/75A/76A toc11
100ms/div, 5V/div
VOUT1
VOUT2
VRST
OUT-OF-PHASE WAVEFORMMAX1858A/75A/76A toc12
1µs/div
VOUT1
20mV/div
VOUT2
20mV/div
12V
VLX1
VLX2
12V
EXTERNALLY SYNCHRONIZED
SWITCHING WAVEFORMMAX1858A/75A/76A toc13
400ns/div
VOUT1
10mV/div
AC-COUPLED
VSYNC
VCK0
VLX1
10V
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
Detailed Description
DC-DC PWM ControllerThe MAX1858A/MAX1875A/MAX1876A step-down con-
verters use a PWM voltage-mode control scheme (Figure
2) for each out-of-phase controller. The controller gener-
ates the clock signal by dividing down the internal oscil-
lator or SYNC input when driven by an external clock, so
each controller’s switching frequency equals half the
oscillator frequency (fSW= fOSC/2). An internal transcon-
ductance error amplifier produces an integrated error
voltage at the COMP pin, providing high DC accuracy.
The voltage at COMP sets the duty cycle using a PWM
comparator and a ramp generator. At each rising edge
of the clock, REG1’s high-side N-channel MOSFET turns
on and remains on until either the appropriate duty cycle
or until the maximum duty cycle is reached. REG2 oper-
ates out-of-phase, so the second high-side MOSFET
turns on at each falling edge of the clock. During each
high-side MOSFET’s on-time, the associated inductor
current ramps up.
During the second-half of the switching cycle, the high-
side MOSFET turns off and the low-side N-channel
MOSFET turns on. Now the inductor releases the stored
energy as its current ramps down, providing current to
the output. Under overload conditions, when the induc-
tor current exceeds the selected valley current limit (see
the Current-Limit Circuit (ILIM_) section), the high-side
MOSFET does not turn on at the appropriate clock edge
and the low-side MOSFET remains on to let the inductor
current ramp down.
Synchronized Out-of-Phase OperationThe two independent regulators in the MAX1858A/
MAX1875A/MAX1876A operate 180°out-of-phase to
reduce input filtering requirements, reduce electromag-
netic interference (EMI), and improve efficiency. This
effectively lowers component cost and saves board
space, making the MAX1858A/MAX1875A/MAX1876A
ideal for cost-sensitive applications.
Dual-switching regulators typically operate both
controllers in-phase, and turn on both high-side
MOSFETs at the same time. The input capacitor must
then support the instantaneous current requirements of
both controllers simultaneously, resulting in increased
ripple voltage and current when compared to a single
switching regulator. The higher RMS ripple current
lowers efficiency due to power loss associated with the
input capacitor’s effective series resistance (ESR). This
typically requires more low-ESR input capacitors in
parallel to minimize input voltage ripple and ESR-related
losses, or to meet the necessary ripple-current rating.
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
MAX1858A/MAX1875A/MAX1876AWith dual, synchronized, out-of-phase operation, the
MAX1858A/MAX1875A/MAX1876As’ high-side MOSFETs
turn on 180°out-of-phase. The instantaneous input cur-
rent peaks of both regulators no longer overlap, resulting
in reduced RMS ripple current and input voltage ripple.
This reduces the required input capacitor ripple-current
rating, allowing fewer or less expensive capacitors, and
reduces shielding requirements for EMI. The Out-of-
Phase Waveforms in the Typical Operating Charac-
teristicsdemonstrate synchronized 180°out-of-phase
operation.
Internal 5V Linear Regulator (VL)All MAX1858A/MAX1875A/MAX1876A functions are
internally powered from an on-chip, low-dropout 5V
regulator. The maximum regulator input voltage (V+) is
23V. Bypass the regulator’s output (VL) with a 4.7µF
ceramic capacitor to PGND. The VLdropout voltage is
typically 500mV, so when V+ is greater than 5.5V, VLis
typically 5V. The MAX1858A/MAX1875A/MAX1876A
also employs an undervoltage lockout circuit that dis-
ables both regulators when VLfalls below 4.2V. VL
should also be bypassed to GND with a 0.1µF capaci-
tor. When VLfalls and UVLO is tripped, the device is
latched and VLmust be discharged below 2.5V before
normal operation can resume.
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
The internal VLlinear regulator can source over 50mA to
supply the IC, power the low-side gate driver, charge the
external boost capacitor, and supply small external
loads. When driving large FETs, little or no regulator cur-
rent may be available for external loads.
For example, when switched at 600kHz, a single large
FET with 18nC total gate charge requires 18nC ✕600kHz
= 11mA. To drive larger MOSFETs, or deliver larger
loads, connect VLto an external power supply from 4.5V
to 5.5V.
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and PORFigure 2. Functional Diagram
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
MAX1858A/MAX1875A/MAX1876A
Dual 180°Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
