Electronic Components Datasheet Search
  English  ▼
ALLDATASHEET.NET

X  

MAX1928EUB25 Datasheet(PDF) 8 Page - Maxim Integrated Products

Part # MAX1928EUB25
Description  Low-Output-Voltage, 800mA, PWM Step-Down DC-DC Converters
Download  12 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  MAXIM [Maxim Integrated Products]
Direct Link  https://www.maximintegrated.com/en.html
Logo MAXIM - Maxim Integrated Products

MAX1928EUB25 Datasheet(HTML) 8 Page - Maxim Integrated Products

Back Button MAX1928EUB25 Datasheet HTML 4Page - Maxim Integrated Products MAX1928EUB25 Datasheet HTML 5Page - Maxim Integrated Products MAX1928EUB25 Datasheet HTML 6Page - Maxim Integrated Products MAX1928EUB25 Datasheet HTML 7Page - Maxim Integrated Products MAX1928EUB25 Datasheet HTML 8Page - Maxim Integrated Products MAX1928EUB25 Datasheet HTML 9Page - Maxim Integrated Products MAX1928EUB25 Datasheet HTML 10Page - Maxim Integrated Products MAX1928EUB25 Datasheet HTML 11Page - Maxim Integrated Products MAX1928EUB25 Datasheet HTML 12Page - Maxim Integrated Products  
Zoom Inzoom in Zoom Outzoom out
 8 / 12 page
background image
Detailed Description
The MAX1927/MAX1928 PWM step-down DC-DC con-
verters accept inputs as low as 2.6V, while delivering
800mA to output voltages as low as 0.75V. These
devices operate in one of two modes to optimize noise
and quiescent current. Under heavy loads, MAX1927/
MAX1928 operate in pulse-width modulation (PWM)
mode and switch at a fixed 1MHz frequency. Under
light loads, they operate in PFM mode to reduce power
consumption. In addition, both devices provide selec-
table forced PWM operation for minimum noise at all
load currents.
PFM Operation and PWM Control Scheme
The PFM mode improves efficiency and reduces quies-
cent current to 140µA at light loads. The MAX1927/
MAX1928 initiate pulse-skipping PFM operation when
the peak inductor current drops below 130mA. During
PFM operation, the MAX1927/MAX1928 switch only as
necessary to service the load, reducing the switching
frequency and associated losses in the internal switch,
synchronous rectifier, and inductor.
During PFM mode, a switching cycle initiates when the
error amplifier senses that the output voltage has
dropped below the regulation point. If the output volt-
age is low, the P-channel MOSFET switch turns on and
conducts current to the output filter capacitor and load.
The PMOS switch turns off when the PWM comparator
is satisfied. The MAX1927/MAX1928 then wait until the
error amplifier senses a low output voltage to start
again. Some jitter is normal during the transition from
PFM to PWM with loads around 100mA. This has no
adverse impact on regulation.
At loads greater than 130mA, the MAX1927/MAX1928
use a fixed-frequency, current-mode, PWM controller
capable of achieving 100% duty cycle. Current-mode
feedback provides cycle-by-cycle current limiting,
superior load and line response, as well as overcurrent
protection for the internal MOSFET and synchronous
rectifier. A comparator at the P-channel MOSFET switch
detects overcurrent conditions exceeding 1.1A.
During PWM operation, the MAX1927/MAX1928 regu-
late output voltage by switching at a constant frequency
and then modulating the power transferred to the load
using the PWM comparator (Figure 1). The error-amp
output, the main switch current-sense signal, and the
slope compensation ramp are all summed at the PWM
comparator. The comparator modulates the output
power by adjusting the peak inductor current during the
first half of each cycle based on the output-error volt-
age. The MAX1927/MAX1928 have relatively low AC-
loop gain coupled with a high-gain integrator to enable
the use of a small, low-valued, output filter capacitor.
The resulting load regulation is 0.3% (typ) from 0 to
800mA.
Forced PWM Operation
To force PWM-only operation, connect PWM to BATT.
Forced PWM operation is desirable in sensitive RF and
data-acquisition applications to ensure that switching
noise does not interfere with sensitive IF and data sam-
pling frequencies. A minimum load is not required dur-
ing forced PWM operation because the synchronous
rectifier passes reverse inductor current as needed to
allow constant frequency operation with no load.
Forced PWM operation has higher quiescent current
than PFM (2mA typ compared to 140µA) due to contin-
uous switching.
100% Duty-Cycle Operation
The maximum on-time can exceed one internal oscilla-
tor cycle, which permits operation at 100% duty cycle.
As the input voltage drops, the duty cycle increases
until the internal P-channel MOSFET stays on continu-
ously. Dropout voltage at 100% duty cycle is the output
current multiplied by the sum of the internal PMOS on-
resistance (typically 0.25
Ω) and the inductor resis-
tance. Near dropout, switching cycles can be skipped,
reducing switching frequency. However, voltage ripple
remains small because the current ripple is still low.
Synchronous Rectification
An N-channel synchronous rectifier eliminates the need
for an external Schottky diode and improves efficiency.
The synchronous rectifier turns on during the second
half of each cycle (off-time). During this time, the volt-
age across the inductor is reversed, and the inductor
current falls. In normal mode, the synchronous rectifier
is turned off when either the output falls out of regula-
tion (and another on-time begins) or when the inductor
current approaches zero. In forced PWM mode, the
synchronous rectifier remains active until the beginning
of a new cycle.
Shutdown Mode
Driving SHDN to GND places the MAX1927/MAX1928
in shutdown mode. In shutdown, the reference, control
circuitry, internal switching MOSFET, and synchronous
rectifier turn off and the output becomes high imped-
ance. Drive SHDN high for normal operation. Input cur-
rent falls to 0.1µA (typ) during shutdown mode.
POK Output
POK is an open-drain output that goes high impedance
20ms after the soft-start ramp has concluded and VFB
is within 90% of the threshold. POK is low impedance
when in shutdown.
Low-Output-Voltage, 800mA, PWM Step-Down
DC-DC Converters
8
_______________________________________________________________________________________


Similar Part No. - MAX1928EUB25

ManufacturerPart #DatasheetDescription
logo
Maxim Integrated Produc...
MAX192 MAXIM-MAX192 Datasheet
201Kb / 24P
   Low-Power, 8-Channel, Serial 10-Bit ADC
Rev 1; 6/02
MAX1920 MAXIM-MAX1920 Datasheet
370Kb / 9P
   Low-Voltage, 400mA Step-Down DC-DC Converters in SOT23
Rev 1; 7/02
MAX1920 MAXIM-MAX1920 Datasheet
93Kb / 8P
   PLASTIC ENCAPSULATED DEVICES
Rev. A April 30, 2003
MAX1920 MAXIM-MAX1920 Datasheet
95Kb / 4P
   fully assembled and tested Evaluation Kit
Rev 0; 03/02
MAX1920 MAXIM-MAX1920 Datasheet
1Mb / 12P
   Low-Voltage, 400mA Step-Down DC-DC Converters in SOT23
2005
More results

Similar Description - MAX1928EUB25

ManufacturerPart #DatasheetDescription
logo
Power Analog Micoelectr...
PAM2301 PAM-PAM2301 Datasheet
902Kb / 13P
   800mA Step-Down DC-DC Converters
logo
Torex Semiconductor
XC6375 TOREX-XC6375 Datasheet
34Kb / 4P
   PWM Controlled, Step down DC/DC Converters
XC9201 TOREX-XC9201 Datasheet
341Kb / 20P
   PWM Controlled Step-Down DC/DC Converters
logo
Richtek Technology Corp...
RT8010B RICHTEK-RT8010B Datasheet
255Kb / 12P
   1.5MHz, 800mA, High Efficiency PWM Step-Down DC/DC Converter
logo
Torex Semiconductor
XC6365 TOREX-XC6365_2 Datasheet
1Mb / 24P
   PWM Controlled, PWM/PFM Switchable Step-Down DC/DC Converters
logo
Micrel Semiconductor
MIC2230 MICREL-MIC2230_10 Datasheet
1Mb / 18P
   Dual Synchronous 800mA/800mA Step-Down DC/DC Regulator
logo
Torex Semiconductor
XC6376 TOREX-XC6376 Datasheet
306Kb / 17P
   PWM Controlled PWM/PFM Switchable Step-down DC/DC Converters
logo
Micrel Semiconductor
MIC2238 MICREL-MIC2238 Datasheet
786Kb / 16P
   Dual Synchronous 800mA/800mA Step-Down DC/DC Regulator
logo
Maxim Integrated Produc...
MAX1733 MAXIM-MAX1733 Datasheet
265Kb / 8P
   Low-Voltage, Step-Down DC-DC Converters in SOT23
19-1586; Rev 0; 7/00
MAX20021 MAXIM-MAX20021_V01 Datasheet
947Kb / 16P
   Automotive Quad, Low-Voltage Step-Down DC-DC Converters
2014
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12


Datasheet Download

Go To PDF Page


Link URL




Privacy Policy
ALLDATASHEET.NET
Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Contact us   |   Privacy Policy   |   Link Exchange   |   Manufacturer List
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com