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PDF MAX8757 Data sheet ( Hoja de datos )
| Número de pieza | MAX8757 | |
| Descripción | (MAX8716 - MAX8757) Dual Power-Supply Controllers | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-3569; Rev 1; 6/05
EVAALVUAAILTAIOBNLEKIT
Interleaved High-Efficiency, Dual Power-Supply
Controllers for Notebook Computers
General Description
The MAX8716/MAX8717/MAX8757 are dual, step-
down, interleaved, fixed-frequency, switch-mode
power-supply (SMPS) controllers with synchronous rec-
tification. They are intended for main (5V/3.3V) and I/O
power generation in battery-powered systems.
Fixed-frequency operation with optimal interleaving
minimizes input ripple current from the lowest input volt-
ages up to the 26V maximum input. Optimal 40/60 inter-
leaving allows the input voltage to go down to 8.3V
before duty-cycle overlap occurs, compared to 180°
out-of-phase regulators where the duty-cycle overlap
occurs when the input drops below 10V.
Accurate output current limit is achieved using a sense
resistor. Alternatively, power dissipation can be
reduced using lossless inductor current sensing.
Independent ON/OFF controls and power-good signals
allow flexible power sequencing. Soft-start reduces
inrush current, while soft-stop gradually ramps the out-
put voltage down preventing negative voltage dips.
A low-noise mode maintains high light-load efficiency
while keeping the switching frequency out of the audi-
ble range.
The MAX8716 is available in a 24-pin thin QFN pack-
age, and the MAX8717/MAX8757 are available in a 28-
pin thin QFN package.
Applications
2 to 4 Li+ Cell Battery-Powered Devices
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Main or I/O Power Supplies
Dual Mode is a trademark of Maxim Integrated Products, Inc.
Features
♦ Fixed 200kHz, 300kHz, or 500kHz Switching
Frequency
♦ No Current-Sense Resistor Required
♦ 40/60 Optimal Interleaving
♦ Reduced Input-Capacitor Requirement
♦ 3.3V and 5V fixed or 1.0V to 5.5V Adjustable
Outputs (Dual Mode™)
♦ 4V to 26V Input Range
♦ Independently Selectable PWM, Skip, and Low-
Noise Mode Operation
♦ Soft-Start and Soft-Stop
♦ 2V Precision Reference with 0.75% Accuracy
♦ Independent Power-Good Outputs
Ordering Information
PART
TEMP RANGE
MAX8716ETG -40°C to +85°C
MAX8716ETG+ -40°C to +85°C
MAX8717ETI -40°C to +85°C
MAX8717ETI+ -40°C to +85°C
MAX8757ETI+ -40°C to +85°C
+Denotes lead-free package.
PIN-PACKAGE
24 Thin QFN 4mm x 4mm
24 Thin QFN 4mm x 4mm
28 Thin QFN 5mm x 5mm
28 Thin QFN 5mm x 5mm
28 Thin QFN 5mm x 5mm
Pin Configurations
TOP VIEW
TOP VIEW
18 17 16 15 14 13
DH1 19
BST1 20
CSH1 21
CSL1 22
FB1 23
PGOOD1 24
MAX8716ETG
12 DH2
11 BST2
10 CSH2
9 CSL2
8 FB2
7 PGOOD2
123 4 56
TQFN
21 20 19 18 17 16 15
DH1 22
14 DH2
BST1 23
13 BST2
CSH1 24
12 CSH2
CSL1 25
FB1 26
MAX8717ETI
MAX8757ETI+
11 CSL2
10 FB2
PGOOD1 27
9 PGOOD2
ILIM1 28
8 ILIM2
123456 7
TQFN
________________________________________________________________ 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  
Interleaved High-Efficiency, Dual Power-Supply
Controllers for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 12V, FSEL = REF, SKIP_ = 0, VON_ = VILIM_ = VCC = VDD = 5V, TA = 0°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.)
PARAMETER
Input Leakage Current
Input Leakage Current
Input Leakage Current
Input Bias Current
SYMBOL
CONDITIONS
SKIP1, SKIP2, FSEL, 0V, or VCC
ILIM1, ILIM2, 0V, or VCC
CSH_, 0V, or VDD
CSL_, 0V, or VDD
MIN TYP MAX UNITS
-3 +3 µA
-0.1
+0.1
µA
-0.1
+0.1
µA
25 50
µA
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VIN = 12V, FSEL = REF, SKIP_ = 0, VON_ = VILIM_ = VCC = VDD = 5V, TA = -40°C to +85°C, unless otherwise
noted.) (Note 6)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
INPUT SUPPLIES
Input Voltage Range
VIN
VBIAS
VCC, VDD
26
V
4.5 5.5
Quiescent Supply Current (VCC)
ICC
CSL_ and FB_ forced above their regulation
points
1.3 mA
Quiescent Supply Current (VDD)
Shutdown Supply Current (VCC)
Shutdown Supply Current (VDD)
MAIN SMPS CONTROLLERS
PWM1 Output Voltage in Fixed
Mode
PWM2 Output Voltage in Fixed
Mode
IDD
CSL_ and FB_ forced above their regulation
points
ON1 = ON2 = GND
ON1 = ON2 = GND
VOUT1
VOUT2
VIN = 6V to 26V, SKIP1 = VCC,
zero to full load (Note 1)
VIN = 6V to 26V, SKIP2 = VCC,
zero to full load (Note 1)
3.255
4.925
5 µA
5 µA
5 µA
3.375
5.105
V
V
Feedback Voltage in Adjustable
Mode
Output Voltage Adjust Range
FB1, FB2 Fixed-Mode Threshold
Voltage
Operating Frequency
Maximum Duty Factor
Minimum On-Time
CURRENT LIMIT
ILIM_ Adjustment Range
VFB_
VIN = 6V to 26V, FB1 or FB2,
duty factor = 20% to 80% (Note 1)
Either SMPS
Dual-mode comparator
fOSC
DMAX
tON(MIN)
FSEL = GND
FSEL = REF (Note 3)
FSEL = VCC
FSEL = GND
FSEL = REF (Note 3)
FSEL = VCC
(Note 4)
0.987
1.0
1.9
170
270
425
97.5
97.5
97.5
0.5
1.023
5.5
2.1
230
330
575
V
V
V
kHz
%
200 ns
VREF
V
_______________________________________________________________________________________ 5
5 Page 
Interleaved High-Efficiency, Dual Power-Supply
Controllers for Notebook Computers
PIN
MAX8716
MAX8717/
MAX8757
11
22
33
44
—5
56
67
—8
79
8 10
9 11
10 12
11 13
12 14
13 15
Pin Description
NAME
FUNCTION
VCC
SKIP1
REF
SKIP2
FSEL
ON1
ON2
ILIM2
PGOOD2
FB2
CSL2
CSH2
BST2
DH2
LX2
Analog Supply Input. Connect to the system supply voltage (+4.5V to +5.5V) through a
series 20Ω resistor. Bypass VCC to AGND with a 1µF or greater ceramic capacitor.
Low-Noise Mode Control for SMPS1. Connect SKIP1 to GND for normal idle-mode
(pulse-skipping) operation or to VCC for PWM mode (fixed frequency). Connect to REF
for low-noise mode.
2.0V Reference Voltage Output. Bypass REF to AGND with a 0.1µF or greater ceramic
capacitor. The reference can source up to 50µA. Loading REF degrades output voltage
accuracy according to the REF load-regulation error (see the Typical Operating
Characteristics). The reference shuts down when both ON1 and ON2 are low.
Low-Noise Mode Control for SMPS2. Connect SKIP2 to GND for normal idle-mode
(pulse-skipping) operation or to VCC for PWM mode (fixed frequency). Connect to REF
for low-noise mode.
Frequency Select Input. This four-level logic input sets the controller’s switching
frequency. Connect FSEL to VCC for 500kHz, to REF for 300kHz, and to GND for 200kHz
operation.
SMPS1 Enable Input. Drive ON1 high to enable SMPS1. Drive ON1 low to shut down
SMPS1.
SMPS2 Enable Input. Drive ON2 high to enable SMPS2. Drive ON2 low to shut down
SMPS2.
SMPS2 Peak Current-Limit Threshold Adjustment. Connect ILIM2 to VCC to enable the
default 50mV current-limit threshold. In adjustable mode, the current-limit threshold
across CSH2 and CSL2 is precisely 1/10th the voltage seen at ILIM2 over a 500mV to
2.0V range. The logic threshold for switchover to the 50mV default value is
approximately VCC - 1V.
SMPS2 Open-Drain Power-Good Output. PGOOD2 is low when SMPS2 is more than
10% below its regulation threshold, during soft-start, and in shutdown.
Feedback Input for SMPS2. Connect FB2 to VCC for fixed 5V output. In adjustable mode,
FB2 regulates to 1V.
Negative Current-Sense Input for SMPS2. Connect to the negative terminal of the
current-sense element. Figure 8 describes two different current-sensing options.
Positive Current-Sense Input for SMPS2. Connect to the positive terminal of the current-
sense element. Figure 8 describes two different current-sensing options.
Boost Flying Capacitor Connection for SMPS2. Connect to an external capacitor and
diode as shown in Figure 1. An optional resistor in series with BST2 allows the DH2 turn-
on current to be adjusted.
High-Side Gate-Driver Output for SMPS2. DH2 swings from LX2 to BST2.
Inductor Connection for SMPS2. Connect LX2 to the switched side of the inductor. LX2
is the lower supply rail for the DH2 high-side gate driver.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet MAX8757.PDF ] | |
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