Electronic Components Datasheet Search
Selected language     English  ▼
Part Name
         Description


MAX877 Datasheet(PDF) 9 Page - Maxim Integrated Products

Part No. MAX877
Description  5V/3.3V/3V/Adjustable-Output, Step-Up/Step-Down DC-DC Converters
Download  12 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  MAXIM [Maxim Integrated Products]
Homepage  http://www.maxim-ic.com
Logo 

 
 9 page
background image
__________Applications Information
Figure 4 shows a MAX877 step-up application circuit.
This circuit starts up and operates with inputs ranging
from 1.0V to 6.2V. Start-up time is a function of the load,
typically less than 5ms. Output current capability is a
function of the input voltage (see
Typical Operating
Characteristics).
The converters will regulate down to the output voltage
and seamlessly switch into boost mode as the input
drops below the output voltage. This is especially use-
ful in battery-powered applications, where the battery
voltage may initially exceed the output voltage. To gen-
erate 5V from four alkaline cells in series, the input
ranges from 6.2V to 3.6V. When the battery pack is
fresh, the MAX877 will step down with the active rectifi-
er acting as the switch. As the batteries approach 5V,
or the desired output voltage, the converter’s control
circuitry will ensure a smooth transition into step-up
mode. The converter operates until the batteries are
less than 3V; efficiency is typically 80% with fresh bat-
teries, and is close to 85% at VIN = 4V.
Inductor Selection
The 22µH inductor shown in the
Typical Operating
Circuit is sufficient for most MAX877/MAX878/MAX879
designs. Other inductor values ranging from 10µH to
47µH are also suitable. The inductor should have a satu-
ration rating equal to or greater than the peak switch-
current limit, which is 1A without an external current limit
(ILIM connected to IN). It is acceptable to operate the
inductor at 120% of its saturation rating; however, this
may slightly reduce efficiency. For highest efficiency,
use an inductor with a low DC resistance, preferably
under 0.2
Ω. Table 1 lists suggested inductor suppliers.
Capacitor Selection
The 100µF, 10V surface-mount tantalum (SMT) output
capacitor shown in the
Typical Operating Circuit will
provide a 25mV output ripple or less, stepping up from
3V to 5V at 200mA. Smaller capacitors, down to 10µF,
are acceptable for light loads or in applications that
can tolerate higher output ripple. The input capacitor
may be omitted if the supply has low output impedance
and the input lead length is less than 2 inches (5cm) or
the loads are small.
The primary factor in selecting both the output and input
filter capacitor is low ESR. The ESR of both bypass and
filter capacitors affects efficiency. Optimize performance
by increasing filter capacitors or using specialized low-
ESR capacitors. The smallest low-ESR SMT tantalum
capacitors currently available are Sprague 595D or 695D
series. Sanyo OS-CON organic-semiconductor through-
hole capacitors also exhibit very low ESR, are rated for
the wide temperature range, and are especially suitable
for operation at cold temperatures (below 0°C).
Table 1 lists suggested capacitor suppliers.
5V/3.3V/3V/Adjustable-Output,
Step-Up/Step-Down DC-DC Converters
_______________________________________________________________________________________
9
INPUT
1.0V TO 6.2V
IN
ILIM
SHDN
100µF
OUTPUT
5V
AGND
MAX877
LX
OUT
PGND
22µH
ON/OFF
22
µF
1
2
7
4
3
6
5
SHDN
PGND
MAX879
OUT
AGND
7
1
3
4
8
6
L1
22
µH
5
LX
FB
2
IN
ILIM
VIN
C1
22µF
R1
C3
C2
100µF
VOUT
R2
Figure 3. MAX879 Adjustable Voltage
Figure 4. MAX877 Standard Application Circuit




Html Pages

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


Datasheet Download



Related Electronics Part Number

Part NumberComponents DescriptionHtml ViewManufacturer
ST763A3.3V STEP DOWN CURRENT MODE PWM DC-DC CONVERTERS 1 2 3 4 5 MoreSTMicroelectronics
IMS77 Watt DC-DC Converters 1 2 3 4 Power-One
NMA-1Isolated 1W Dual Output DC-DC Converters 1 2 C&D Technologies
IRF7811WPower MOSFET for DC-DC Converters 1 2 3 4 5 MoreInternational Rectifier
MAX1674High-Efficiency Low-Supply-Current Compact Step-Up DC-DC Converters 1 2 3 4 5 MoreMaxim Integrated Products
MAX5025500kHz 36V Output SOT23 PWM Step-Up DC-DC Converters 1 2 3 4 5 MoreMaxim Integrated Products
SP6122Low Voltage Micro 8 PFET Buck Controller Ideal for 1A to 5A Small Footprint DC-DC Power Converters 1 2 3 4 5 MoreSipex Corporation
PTH05050DC-DC CONVERTERS POLA Non-isolated 1 2 3 4 Artesyn Technologies
71128Simple Solution for Dynamically Programming the Output Voltage of DC-DC Converters 1 2 3 4 5 MoreVishay Siliconix
NXI15081 A DC-DC Non-Isolated Converters 1 2 3 Artesyn Technologies

Link URL

Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Bookmark   |   Link Exchange   |   Manufacturer List
All Rights Reserved© Alldatasheet.com 2003 - 2017    


Mirror Sites
English : Alldatasheet.com  , 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