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PDF MAX8640Y Data sheet ( Hoja de datos )
| Número de pieza | MAX8640Y | |
| Descripción | 4MHz/2MHz Synchronous Step-Down DC-DC Converters | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-3997; Rev 4; 2/09
EVAALVUAAILTAIOBNLEKIT
Tiny 500mA, 4MHz/2MHz Synchronous
Step-Down DC-DC Converters
General Description
The MAX8640Y/MAX8640Z step-down converters are
optimized for applications where small size, high effi-
ciency, and low output ripple are priorities. They utilize
a proprietary PWM control scheme that optimizes the
switching frequency for high efficiency with small exter-
nal components and maintains low output ripple volt-
age at all loads. The MAX8640Z switches at up to
4MHz to allow a tiny 1µH inductor and 2.2µF output
capacitor. The MAX8640Y switches at up to 2MHz for
higher efficiency while still allowing small 2.2µH and
4.7µF components. Output current is guaranteed up to
500mA, while typical quiescent current is 28µA.
Factory-preset output voltages from 0.8V to 2.5V elimi-
nate external feedback components.
Internal synchronous rectification greatly improves effi-
ciency and replaces the external Schottky diode
required in conventional step-down converters. Internal
fast soft-start eliminates inrush current so as to reduce
input capacitor requirements.
The MAX8640Y/MAX8640Z are available in the tiny 6-
pin, SC70 (2.0mm x 2.1mm) and µDFN (1.5mm x
1.0mm) packages. Both packages are lead-free.
Applications
Microprocessor/DSP Core Power
I/O Power
Cell Phones, PDAs, DSCs, MP3s
Other Handhelds Where Space Is Limited
www.DataSheet4U.com
Typical Operating Circuit
INPUT
2.7V TO 5.5V
C1
2.2μF
ON/OFF
L1
1μH OR 2.2μH
OUTPUT
0.8V TO 2.5V
UP TO 500mA
IN LX
MAX8640Y
GND MAX8640Z OUT
SHDN
C2
2.2μF OR
4.7μF
Features
♦ Tiny SC70 and µDFN Packages
♦ 500mA Guaranteed Output Current
♦ 4MHz or 2MHz PWM Switching Frequency
♦ Tiny External Components: 1µH/2.2µF or
2.2µH/4.7µF
♦ 28µA Quiescent Current
♦ Factory Preset Outputs from 0.8V to 2.5V
♦ ±1% Initial Accuracy
♦ Low Output Ripple at All Loads
♦ Ultrasonic Skip Mode Down to 1mA Loads
♦ Ultra-Fast Line- and Load-Transient Response
♦ Fast Soft-Start Eliminates Inrush Current
Ordering Information
PART*
PIN-
PACKAGE
TOP MARK
MAX8640YEXT08+T
6 SC70
ACQ
MAX8640YEXT10+T
6 SC70
ADF
MAX8640YEXT11+T
6 SC70
ACR
MAX8640YEXT12+T
6 SC70
ACS
MAX8640YEXT13+T
6 SC70
ACG
MAX8640YEXT15+T
6 SC70
ADD
MAX8640YEXT16+T
6 SC70
ADB
MAX8640YEXT18+T
6 SC70
ACI
MAX8640YEXT19+T
6 SC70
ACH
MAX8640YEXT82+T
6 SC70
ADJ
*Contact factory for availability of each version. For 2.85V output
(82 version), request application note that includes limitations
and typical operating characteristics.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Note: All devices are specified over the -40°C to +85°C
operating temperature range.
Ordering Information continued and Selector Guide appears
at end of data sheet.
Pin Configurations
+
LX 1
TOP VIEW
+
6 IN
LX 1
6
MAX8640Y
GND 2 MAX8640Z 5 GND
MAX8640Y
GND 2 MAX8640Z 5
IN
GND
OUT 3
4 SHDN OUT 3
4 SHDN
SC70
2.0mm x 2.1mm
μDFN
1.5mm x 1.0mm
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
1 page  
Tiny 500mA, 4MHz/2MHz Synchronous
Step-Down DC-DC Converters
Pin Description
PIN NAME
FUNCTION
1
LX
Inductor Connection to the Internal Drains of the p-channel and n-channel MOSFETs. High impedance
during shutdown.
2, 5 GND Ground. Connect these pins together directly under the IC.
3
OUT
Output Sense Input. Bypass with a ceramic capacitor as close as possible to pin 3 (OUT) and pin 2 (GND).
OUT is internally connected to the internal feedback network.
4
SHDN Active-Low Shutdown Input. Connect to IN or logic-high for normal operation. Connect to GND or logic-low for
shutdown mode.
Supply Voltage Input. Input voltage range is 2.7V to 5.5V. Bypass with a ceramic capacitor as close as
6 IN possible to pin 6 (IN) and pin 5 (GND).
Detailed Description
The MAX8640Y/MAX8640Z step-down converters deliv-
er over 500mA to outputs from 0.8V to 2.5V. They utilize
a proprietary hysteretic PWM control scheme that
switches at up to 4MHz (MAX8640Z) or 2MHz
(MAX8640Y), allowing some trade-off between efficien-
cy and size of external components. At loads below
100mA, the MAX8640Y/MAX8640Z automatically switch
to pulse-skipping mode to minimize the typical quies-
cent current (28µA). Output ripple remains low at all
loads, while the skip-mode switching frequency
remains ultrasonic down to 1mA (typ) loads. Figure 1 is
the simplified functional diagram.
Control Scheme
A proprietary hysteretic PWM control scheme ensures
www.DahtaigShheeeftf4iUci.econmcy, fast switching, fast transient response,
low output ripple, and physically tiny external compo-
nents. This control scheme is simple: when the output
voltage is below the regulation threshold, the error
comparator begins a switching cycle by turning on the
high-side switch. This switch remains on until the mini-
mum on-time expires and the output voltage is above
the regulation threshold or the inductor current is above
the current-limit threshold. Once off, the high-side
switch remains off until the minimum off-time expires
and the output voltage falls again below the regulation
threshold. During the off period, the low-side synchro-
nous rectifier turns on and remains on until either the
high-side switch turns on again or the inductor current
approaches zero. The internal synchronous rectifier
eliminates the need for an external Schottky diode.
Voltage-Positioning Load Regulation
The MAX8640Y/MAX8640Z utilize a unique feedback
network. By taking DC feedback from the LX node, the
usual phase lag due to the output capacitor is
removed, making the loop exceedingly stable and
IN
SHDN
PWM
LOGIC
LX
GND
MAX8640Y
MAX8640Z
0.6V
OUT
Figure 1. Simplified Functional Diagram
allowing the use of very small ceramic output capacitors.
This configuration yields load regulation equal to the
inductor’s series resistance multiplied by the load current.
This voltage-positioning load regulation greatly reduces
overshoot during load transients, effectively halving the
peak-to-peak output-voltage excursions compared to tra-
ditional step-down converters. See the Load-Transient
Response in the Typical Operating Characteristics.
Shutdown Mode
Connecting SHDN to GND or logic low places the
MAX8640Y/MAX8640Z in shutdown mode and reduces
supply current to 0.1µA (typ). In shutdown, the control
circuitry and internal MOSFET switches turn off and LX
becomes high impedance. Connect SHDN to IN or
logic high for normal operation.
_______________________________________________________________________________________ 5
5 Page 
Tiny 500mA, 4MHz/2MHz Synchronous
Step-Down DC-DC Converters
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
www.DataSheet4U.com
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MAX8640Y.PDF ] | |
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