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PDF MAX1820 Data sheet ( Hoja de datos )
| Número de pieza | MAX1820 | |
| Descripción | (MAX1829 / MAX1821) W-cdma Cellular Phone 600mA Buck Regulators | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX1820 (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
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19-2011; Rev 2; 7/02
www.DataESVhAeAeLVtU4AAUILT.AcIOoBmNLEKIT
WCDMA Cellular Phone 600mA
Buck Regulators
General Description
The MAX1820/MAX1821 low-dropout, pulse-width-mod-
ulated (PWM) DC-DC buck regulators are optimized to
provide power to the power amplifier (PA) in WCDMA
cell phones; however, they may be applied in many
other applications where high efficiency is a priority. The
supply voltage range is from 2.6V to 5.5V, and the guar-
anteed output current is 600mA; 1MHz PWM switching
allows for small external components, while skip mode
reduces quiescent current to 180µA with light loads.
The MAX1820 is dynamically controlled to provide vary-
ing output voltages from 0.4V to 3.4V. The circuit is
designed such that the output voltage settles in <30µs
for a full-scale change in voltage and current. The
MAX1821 is set with external resistors to provide any
fixed output voltage in the 1.25V to 5.5V range.
The MAX1820/MAX1821 include a low on-resistance
internal MOSFET switch and synchronous rectifier to
maximize efficiency and minimize external component
count; 100% duty-cycle operation allows for low dropout
of only 150mV at 600mA load, including the external
inductor resistance. The devices are offered in 10-pin
µMAX and tiny 3 ✕ 4 chip-scale (UCSP™) packages.
________________________Applications
WCDMA Cell Phone Power Amplifiers
PDA, Palmtop, and Notebook Computers
Microprocessor Core Supplies
Digital Cameras
PCMCIA and Network Cards
Hand-Held Instruments
Typical Operating Circuits continued at end of data sheet.
Ordering Information continued at end of data sheet.
Pin Configurations appear at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
Features
o Dynamically Adjustable Output from 0.4V to 3.4V
(MAX1820)
o Programmable Output from 1.25V to 5.5V
(MAX1821)
o SYNC to 13MHz External Clock (MAX1820X)
o SYNC to 19.8MHz External Clock (MAX1820Y)
o NO SYNC, Internal 1MHz Oscillator (MAX1820Z)
o Low Quiescent Current
180µA (typ) in Skip Mode
0.1µA (typ) in Shutdown Mode
o No External Schottky Diode Required
o 600mA Guaranteed Output Current
o 0% to 100% Duty-Cycle Operation
o 150mV Dropout at 600mA Load (Including RDC
of External Inductor)
o µMAX or UCSP Packaging
Typical Operating Circuits
INPUT
2.6V TO
5.5V
13MHz
OR
19.8MHz
VOUT CONTROL
DAC
BATT
SHDN
LX
OUT
PGND
MAX1820
SYNC COMP
4.7µH
REF
SKIP
GND
DYNAMIC
OUTPUT
0.4V TO 3.4V
4.7µF
Ordering Information
PART
SYNC
OUTPUT VOLTAGE
FREQ (MHz)
TEMP RANGE
PIN-PACKAGE
UCSP MARK
MAX1820ZEBC*
No Sync
Dynamic
-40°C to +85°C
3 ✕ 4 UCSP
AAB
MAX1820YEBC*
19.8
Dynamic
-40°C to +85°C
3 ✕ 4 UCSP
AAL
MAX1820XEBC*
13
Dynamic
-40°C to +85°C
3 ✕ 4 UCSP
AAM
MAX1820ZEUB
No Sync
Dynamic
-40°C to +85°C
10 µMAX
—
MAX1820YEUB
19.8
Dynamic
-40°C to +85°C
10 µMAX
—
MAX1820XEUB
13
Dynamic
-40°C to +85°C
10 µMAX
—
*UCSP reliability is integrally linked to the user’s assembly methods, circuit board material, and environment. Refer to the UCSP
Reliability Notice in the UCSP Reliability section of this data sheet for more information.
________________________________________________________________ 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  
w w w . D a t a S h e e t 4 U . c o m WCDMA Cellular Phone 600mA
Buck Regulators
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 3.6V, SHDN = BATT, SKIP = SYNC = GND, VREF = 1.25V (MAX1820 only), TA = -40°C to +85°C, unless otherwise noted.)
(Notes 2, 3)
PARAMETER
LX Leakage Current
Maximum Duty Cycle
Minimum Duty Cycle
SYNC AND OSCILLATOR
SYNC Divide Ratio
(MAX1820X)
SYNC Capture Range
(MAX1820X)
SYNC Divide Ratio
(MAX1820Y)
SYNC Capture Range
(MAX1820Y)
SYNC Leakage Current
SYMBOL
ILX
dutyMAX
dutyMIN
CONDITIONS
VBATT = 5.5V, LX = GND or BATT
SKIP = GND
SKIP = BATT, VBATT = 4.2V
ISYNC
SYNC = sine wave, SYNC input = 200mVP-P
SYNC = sine wave, SYNC input = 800mVP-P
SYNC = sine wave, AC-coupled,
SYNC input = 500mVP-P
SYNC = sine wave, SYNC input = 200mVP-P
SYNC = sine wave, SYNC input = 800mVP-P
SYNC = sine wave, AC-coupled,
SYNC input = 500mVP-P
VSYNC = IV (MAX1820Z, MAX1821)
VSYNC = IV (MAX1820X, MAX1820Y, and
MAX1821X)
MIN
-1
100
13
13
10
18
18
15
-1
-5
MAX
1
0
10
UNITS
µA
%
%
13
Hz/Hz
13
16 MHz
18
Hz/Hz
18
21 MHz
+1
µA
+5
Internal Oscillator Frequency
(MAX1820Z, MAX1821)
fOSC
SYNC = GND
0.8 1.2 MHz
LOGIC INPUTS (SKIP, SHDN)
Logic Input High
Logic Input Low
Logic Input Current
VIH
VIL
1.6 V
0.4 V
1 µA
Note 2: Limits are 100% production tested at TA = +25°C for UCSP parts. Limits over the entire operating temperature range are
guaranteed by design and characterization but are not production tested.
Note 3: Specifications to -40°C are guaranteed by design and not subject to production test.
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT VOLTAGE
(NORMAL MODE, VIN = 3.6V)
100
RLOAD = 5Ω
90
RLOAD = 10Ω
80
RLOAD = 15Ω
70
EFFICIENCY vs. OUTPUT VOLTAGE
(PWM MODE, VIN = 3.6V)
100
RLOAD = 5Ω
90
RLOAD = 10Ω
80
RLOAD = 15Ω
70
EFFICIENCY vs. INPUT VOLTAGE
NORMAL MODE, RLOAD = 10Ω
100
90
80
VOUT = 1.8V
VOUT = 3.4V
70
60
50 VOUT = 0.4V
60 60
40
30
50 50
20
10
40
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
OUTPUT VOLTAGE (V)
40
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
OUTPUT VOLTAGE (V)
0
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
VIN (V)
_______________________________________________________________________________________ 5
5 Page 
www.DataSheet4U.com
WCDMA Cellular Phone 600mA
Buck Regulators
VIN = 2.6V TO 5.5V
10µF
0.1µF
0.047µF
BATT LX
SHDN MAX1821 PGND
SYNC
REF
FB
COMP
SKIP GND
4.7µH
4.7µF
VOUT = 1.5V
R1
6kΩ
RC
82kΩ
C1
330pF
R2
30kΩ
C2*
1pF
* CAN BE OMITTED IF CERAMIC OUTPUT CAPACITOR IS USED.
Figure 3. Standard Operating Circuit
the load. The duty cycle of a buck step-down converter
is ideally a ratio of the output voltage to input voltage in
steady-state condition.
The MAX1820/MAX1821 have internal switch current
limits of 1.2A (typ). If ILX exceeds this maximum, the
high-side FET turns off and the synchronous rectifier
turns on. This lowers the duty cycle and causes the out-
put voltage to droop as long as the load current
remains excessive. There is also a synchronous rectifier
current limit of -0.85A when the device is operating in
forced PWM mode (see the Forced PWM Operation sec-
tion). If the negative current limit is exceeded, the syn-
chronus rectifier is turned off, and the inductor current
continues to flow through its body diode until the begin-
ning of the next cycle or the inductor current drops to
zero. This means there is a limit on how much current
the device is allowed to shuttle in response to output
power reduction.
Normal Mode Operation
Connecting SKIP to GND enables MAX1820/MAX1821
normal operation (Figure 3). This allows automatic PWM
control at medium and heavy loads and skip mode at
light loads to improve efficiency and reduce quiescent
current to 180µA. Operating in normal mode also allows
the MAX1820/MAX1821 to pulse skip when the peak
inductor current drops below 130mA, corresponding to
a load current of approximately 65mA.
During skip operation, the MAX1820/MAX1821 switch
only as needed to service the load, reducing the
switching frequency and associated losses in the inter-
nal switch, the synchronous rectifier, and the external
inductor.
There are three steady-state operating conditions for
the MAX1820/MAX1821 in normal mode. The device
performs in continuous conduction for heavy loads in a
manner identical to forced PWM mode. The inductor
current becomes discontinuous at medium loads,
requiring the synchronous rectifier to be turned off
before the end of a cycle as the inductor current reach-
es zero. The device enters into skip mode when the
converter output voltage exceeds its regulation limit
before the inductor current reaches its skip thres-
hold level.
During skip mode, a switching cycle initiates when the
output voltage has dropped out of regulation. The P-
channel MOSFET switch turns on and conducts current
to the output-filter capacitor and load until the inductor
current reaches the skip peak current limit. Then the
main switch turns off, and the magnetic field in the
inductor collapses, while current flows through the syn-
chronous rectifier to the output filter capacitor and the
load. The synchronous rectifier is turned off when the
inductor current reaches zero. The MAX1820/ MAX1821
wait until the skip comparator senses a low output volt-
age again.
Forced PWM Operation
Connect SKIP to BATT for forced PWM operation.
Forced PWM operation is desirable in sensitive RF and
data-acquisition applications to ensure that switching
harmonics do not interfere with sensitive IF and data-
sampling frequencies. A minimum load is not required
during forced PWM operation since the synchronous
rectifier passes reverse-inductor current as needed to
allow constant-frequency operation with no load.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet MAX1820.PDF ] | |
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