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PDF MAX1761 Data sheet ( Hoja de datos )
| Número de pieza | MAX1761 | |
| Descripción | Small / Dual / High-Efficiency Buck Controller for Notebooks | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX1761 (archivo pdf) en la parte inferior de esta página. Total 23 Páginas | ||
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19-1835; Rev 0; 10/00
EVAALVUAAILTAIOBNLEKIT
Small, Dual, High-Efficiency
Buck Controller for Notebooks
General Description
The MAX1761 dual pulse-width-modulation (PWM),
step-down controller provides high efficiency, excellent
transient response, and high DC output accuracy in an
extremely compact circuit topology. These features are
essential for stepping down high-voltage batteries to
generate low-voltage CPU core, I/O, and chipset RAM
supplies in PC board area critical applications, such as
notebook computers and smart phones.
Maxim’s proprietary Quick-PWM™ quick-response,
constant-on-time PWM control scheme handles wide
input/output voltage ratios with ease and provides
“instant-on” response to load transients while maintain-
ing a relatively constant switching frequency.
The MAX1761 achieves high efficiency at reduced cost
by eliminating the current-sense resistor found in tradi-
tional current-mode PWMs. Efficiency is further
enhanced by its ability to drive large synchronous-recti-
fier MOSFETs. The MAX1761 employs a complemen-
tary MOSFET output stage, which reduces component
count by eliminating external bootstrap capacitors and
diodes.
Single-stage buck conversion allows this device to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, two-stage conversion
(stepping down the +5V system supply instead of the
battery) at a higher switching frequency allows the mini-
mum possible physical size.
The MAX1761 is intended for CPU core, chipset,
DRAM, or other low-voltage supplies. The MAX1761 is
available in a 16-pin QSOP package. For applications
requiring greater output power, refer to the MAX1715
data sheet. For a single-output version, refer to the
MAX1762/MAX1791 data sheet.
________________________Applications
Notebooks and PDAs
Digital Cameras
Handy-Terminals
Smart Phones
1.8V/2.5V Logic and I/O Supplies
Quick-PWM and Dual Mode are trademarks of
Maxim Integrated Products.
Features
o Free-Running On-Demand PWM
o Selectable Light-Load Pulse-Skipping Operation
o ±1% Total DC Error in Forced-PWM Mode
o 5V to 20V Input Range
o Flexible Output Voltages
OUT1: Dual Mode™ Fixed 2.5V or 1V to 5.5V
Adjustable
OUT2: Dual Mode Fixed 1.8V or 1V to 5.5V
Adjustable
o Output Undervoltage Protection
o Complementary Synchronous Buck
o No Current-Sense Resistor
o 4.65V at 25mA Linear Regulator Output
o 4µA V+ Shutdown Supply Current
o 5µA VL Shutdown Supply Current
o 950µA Quiescent Supply Current
o Tiny 16-Pin QSOP Package
PART
MAX1761EEE
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
16 QSOP
Pin Configuration
TOP VIEW
FB1 1
OUT1 2
REF 3
ON2 4
V+ 5
ON1 6
OUT2 7
FB2 8
MAX1761
QSOP
16 DH1
15 CS1
14 DL1
13 VL
12 GND
11 DL2
10 CS2
9 DH2
________________________________________________________________ Maxim Integrated Products 1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
Small, Dual, High-Efficiency
Buck Controller for Notebooks
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = 15V, CVL = 4.7µF, CREF = 0.1µF, VL not externally driven unless otherwise noted, TA = -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
GATE DRIVERS
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
DH_ Gate Driver On-Resistance
(Pullup)
V+ = 6V to 20V, DH_, high state
8Ω
DH_ Gate Driver On-Resistance
(Pulldown)
DH_, low state
10 Ω
DL_ Gate Driver On-Resistance
(Pullup)
DL_, high state
8Ω
DL_ Gate Driver On-Resistance
(Pulldown)
DL_, low state
5Ω
DH_ Gate Driver Source/Sink
Current
DL_ Gate Drive Sink Current
DL_ Gate Driver Source Current
LOGIC CONTROLS
ON_ Logic Input High Voltage
ON2 Logic Input Float Voltage
(Forced-PWM Mode)
ON_ Logic Input Low Voltage
ON1 Logic Input Current
ON2 Logic High Input Current
ON2 Logic Low Input Current
FB_ Dual Mode Threshold
VDH_ = 3V, V+ = 6V
VDL_ = 2.5V
VDL_ = 2.5V
VON1 > 2.0V
VON2 > 2.0V
VON2 < 0.5V, VON1 > 2.0V
2.05
1.3
-1
0
-2
50
1.95
0.5
1
3
0
150
A
A
A
V
V
V
µA
µA
µA
mV
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
Note 2: If V+ is less than 5V, V+ must be connected to VL. If VL is connected to V+, V+ must be between 4.5V and 5.5V.
Note 3: DC output accuracy specifications refer to the trip-level error of the error amplifier. The output voltage will have a DC regula-
tion higher than the trip level by 50% of the ripple. In PFM mode, the output will rise by approximately 1.5% when transition-
ing from continuous conduction to no load.
Note 4: One-shot times are measured at the DH pin (V+ = 15V, CDH = 400pF, 90% point to 90% point). Actual in-circuit times may
be different due to MOSFET switching speeds.This effect can also cause the switching frequency to vary.
_______________________________________________________________________________________ 5
5 Page 
Small, Dual, High-Efficiency
Buck Controller for Notebooks
VL
CL
OUT1
CIN1
Q1
OUT1
COUT1
L1
D1 Q2
ON1
VIN
VL LINEAR
REG
VIN
2V
VREF
REF
V+
DL1
DH1
DRIVER
MAX1761
VIN
ON1
DH
ZCC1
PWM
CONTROL
BLOCK
ZERO
CROSSING
DH
PWM
CONTROL
BLOCK
ZERO
CROSSING
ZCC2
DH2
DH2
DRIVER
CS1
-0.1V
DL1
DL1
DRIVER
ILIM1
ILIM
VL
DL
ILIM
ILIM2
CS2
VOS
-0.1V
VL
DL2
DL2
DL
DRIVER
OUT1
ON1
OUT
SHDN
GND
OUT
SHDN
OUT2
ON2
REF
CREF
VIN
CIN2
Q3
L2
Q4 D2
OUT2
COUT2
ON2
Figure 2. Functional Diagram
On-Time One-Shot
The heart of the PWM core is the one-shot that sets the
high-side switch on-time for both controllers. This fast,
low-jitter, adjustable one-shot includes circuitry that
varies the on-time in response to battery and output
voltage. The high-side switch on-time is inversely pro-
portional to the battery voltage as measured by the V+
input, and proportional to the output voltage. This algo-
rithm results in a nearly constant switching frequency
despite the absence of a fixed-frequency clock genera-
tor. The benefits of a constant switching frequency are
Table 3. On-Time One-Shot
DEVICE
OUT1
OUT2
K
(µs)
2.857
4.000
MIN
(kHz)
318
227
TYP
(kHz)
350
250
MAX
(kHz)
428
278
twofold: first, the switching noise occurs at a known fre-
quency and is easily filtered; second, the inductor rip-
ple current remains relatively constant, resulting in
predictable output voltage ripple and a relatively sim-
ple design procedure. The difference in frequencies
between OUT1 and OUT2 prevents audio-frequency
“beating” and minimizes crosstalk between the two
SMPS. The on-times can be calculated by using the
equation below that references the K values listed in
Table 3.
On - Time
=
K
VOUT_ +
VIN
0.1V
The 0.1V offset term accounts for the expected drop
across the low-side MOSFET switch.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet MAX1761.PDF ] | |
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