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PDF MAX1858 Data sheet ( Hoja de datos )
| Número de pieza | MAX1858 | |
| Descripción | Dual 180 Out-of-Phase PWM Step-Down Controller with Power Sequencing and POR | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX1858 (archivo pdf) en la parte inferior de esta página. Total 22 Páginas | ||
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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.
1 page  
Dual 180° Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 12V, TA = +25°C, unless otherwise noted.)
START AND STOP WAVEFORM
(MAX1875A/MAX1876A ONLY)
10VMAX1858A/75A/76A toc09
EN
0V
VOUT1
1V/div
IOUT1 = 300mA
0V
PREBIAS STARTUP
VOUT2
1V/div
IOUT2 = 300mA
0V
2ms/div
OUT-OF-PHASE WAVEFORM
MAX1858A/75A/76A toc12
VOUT1
20mV/div
12V
VLX1
0V
12V
VLX2
0V
VOUT2
20mV/div
INPUT POWER REMOVAL
MAX1858A/75A/76A toc10
VIN
10V/div
0V
VOUT1
1V/div
IOUT1 = 300mA
0V
VOUT2
1V/div
IOUT2 = 300mA
0V
5ms/div
EXTERNALLY SYNCHRONIZED
SWITCHING WAVEFORM
5VMAX1858A/75A/76A toc13
VSYNC
0V
5V
VCK0
0V
10V
VLX1
0V
VOUT1
10mV/div
AC-COUPLED
RESET TIMEOUT
(MAX1858A/MAX1876A ONLY)
MAX1858A/75A/76A toc11
100ms/div, 5V/div
EN
0
VOUT2
0V
VOUT1
0V
VRST
0V
CKO OUTPUT WAVEFORM
MAX1858A/75A/76A toc14
SYNC = GND
5V
VCK0
0V
10V
VLX1
0V
VOUT1
10mV/div
AC-COUPLED
1µs/div
400ns/div
400ns/div
CKO OUTPUT WAVEFORM
MAX1858A/75A/76A toc15
SYNC = VL
5V
VCK0
0V
10V
VLX1
0V
VOUT1
10mV/div
400ns/div
SHORT-CIRCUIT CURRENT FOLDBACK
AND RECOVERY
MAX1858A/75A/76A toc16
IOUT1 = 10A (5A/div)
VOUT1 = 1.8V (1V/div)
SHORT
VOUT2
VOUT2 = 2.5V (1V/div)
IOUT2 = 10A (5A/div)
4ms/div
_______________________________________________________________________________________ 5
5 Page 
Dual 180° Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
UVLO
VL
EN
A
VOUT1
SS1
VOUT2
SS2
DH1
DL1
DH2
DL2
BC
D
E
FG
H
I JK
LM
N
MAX1858A POWER-ON-OFF SEQUENCING DEFINITIONS
SYMBOL
UVLO
VL
EN
VOUT1
SS1
VOUT2
SS2
DH1
DL1
DH2
DL2
A
B
C
DEFINITION
Undervoltage threshold value is provided in the
Electrical Characteristics table.
Internal 5V Linear-Regulator Output
Active-High Enable Input
Regulator 1 Output Voltage
Regulator 1: Internal Soft-Start Input Signal into Error Amplifier
Regulator 2 Output Voltage
Regulator 2: Internal Soft-Start Input Signal into Error Amplifier
Regulator 1: High-Side Gate-Driver Output
Regulator 1: Low-Side Gate-Driver Output
Regulator 2: High-Side Gate-Driver Output
Regulator 2: Low-Side Gate-Driver Output
VL rising while below the UVLO threshold. EN is low.
VL is greater than the UVLO threshold. EN is low.
EN is pulled high. DH1 and DL1 start switching. DH2 and
DL2 are off.
O
SYMBOL
D
E
F
G
H
I
J
K
L
M
N
O
P
P
DEFINITION
Normal operation
VL enters UVLO.
VL exits UVLO.
Resumes normal operation. DH1 and DL1 start switching.
DH2 and DL2 are off.
EN is pulled low and then high.
VOUT1 must reach 0V before restarting due to the cycling
of the enable in region H (above).
VOUT1 recovers.
VOUT2 recovers.
VL enters UVLO before VOUT2 fully recovers.
VL exits UVLO.
UVLO latches DL_ low.
Exiting UVLO: DL_ remains latched low until the first fall
of DH_ is detected.
DL_ is high after EN is pulled low and soft-stop is complete.
Figure 4. MAX1858A Detailed Power-On-Off Sequencing
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet MAX1858.PDF ] | |
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