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PDF MAX1635 Data sheet ( Hoja de datos )
| Número de pieza | MAX1635 | |
| Descripción | Multi-Output / Low-Noise Power-Supply Controllers for Notebook Computers | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX1635 (archivo pdf) en la parte inferior de esta página. Total 28 Páginas | ||
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19-0480; Rev 3; 4/97
EVAALVUAAILTAIOBNLEKIT Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
________________General Description
The MAX1630–MAX1635 are buck-topology, step-down,
switch-mode, power-supply controllers that generate
logic-supply voltages in battery-powered systems. These
high-performance, dual/triple-output devices include on-
board power-up sequencing, power-good signaling with
delay, digital soft-start, secondary winding control, low-
dropout circuitry, internal frequency-compensation net-
works, and automatic bootstrapping.
Up to 96% efficiency is achieved through synchronous
rectification and Maxim’s proprietary Idle Mode™ control
scheme. Efficiency is greater than 80% over a 1000:1
load-current range, which extends battery life in system-
suspend or standby mode. Excellent dynamic response
corrects output load transients caused by the latest
dynamic-clock CPUs within five 300kHz clock cycles.
Strong 1A on-board gate drivers ensure fast external
N-channel MOSFET switching.
These devices feature a logic-controlled and synchroniz-
able, fixed-frequency, pulse-width-modulation (PWM)
operating mode. This reduces noise and RF interference
in sensitive mobile communications and pen-entry appli-
cations. Asserting the SKIP pin enables fixed-frequency
mode, for lowest noise under all load conditions.
The MAX1630–MAX1635 include two PWM regulators,
adjustable from 2.5V to 5.5V with fixed 5.0V and 3.3V
modes. All these devices include secondary feedback
regulation, and the MAX1630/MAX1632/MAX1633/
MAX1635 each contain 12V/120mA linear regulators. The
MAX1631/MAX1634 include a secondary feedback input
(SECFB), plus a control pin (STEER) that selects which
PWM (3.3V or 5V) receives the secondary feedback sig-
nal. SECFB provides a method for adjusting the sec-
ondary winding voltage regulation point with an external
resistor divider, and is intended to aid in creating auxiliary
voltages other than fixed 12V.
The MAX1630/MAX1631/MAX1632 contain internal out-
put overvoltage and undervoltage protection features.
________________________Applications
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Desktop CPU Local DC-DC Converters
____________________________Features
o 96% Efficiency
o +4.2V to +30V Input Range
o 2.5V to 5.5V Dual Adjustable Outputs
o Selectable 3.3V and 5V Fixed or Adjustable
Outputs (Dual Mode™)
o 12V Linear Regulator
o Adjustable Secondary Feedback
(MAX1631/MAX1634)
o 5V/50mA Linear Regulator Output
o Precision 2.5V Reference Output
o Programmable Power-Up Sequencing
o Power-Good (RESET) Output
o Output Overvoltage Protection
(MAX1630/MAX1631/MAX1632)
o Output Undervoltage Shutdown
(MAX1630/MAX1631/MAX1632)
o 200kHz/300kHz Low-Noise, Fixed-Frequency
Operation
o Low-Dropout, 99% Duty-Factor Operation
o 2.5mW Typical Quiescent Power (+12V input, both
SMPSs on)
o 4µA Typical Shutdown Current
o 28-Pin SSOP Package
_______________Ordering Information
PART
TEMP. RANGE PIN-PACKAGE
MAX1630CAI
0°C to +70°C
28 SSOP
MAX1630EAI
-40°C to +85°C
28 SSOP
Ordering Information continued on last page.
________________Functional Diagram
INPUT
+5V (RTC)
5V
LINEAR
12V
LINEAR
+12V
+3.3V
3.3V
SMPS
5V
SMPS
+5V
Pin Configurations and Selector Guide appear at end of data
sheet.
Idle Mode and Dual Mode are trademarks of Maxim Integrated
Products.
ON/OFF
POWER-UP POWER-
SEQUENCE GOOD
RESET
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
1 page  
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
__________________________________________Typical Operating Characteristics
(Circuit of Figure 1, 3A Table 1 components, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. 5V OUTPUT CURRENT
100
V+ = 6V
90
V+ = 15V
80
70
EFFICIENCY vs. 3.3V OUTPUT CURRENT
100
V+ = 6V
90
80
V+ = 15V
70
MAX1632/MAX1635
MAXIMUM 15V VDD OUTPUT
CURRENT vs. SUPPLY VOLTAGE
800
VDD > 13V
5V REGULATING
600 5V LOAD = 0A
400
5V LOAD = 3A
60
50
0.001
ON5 = 5V
ON3 = 0V
f = 300kHz
MAX1631/MAX1634
0.01 0.1
1
5V OUTPUT CURRENT (A)
10
60
50
0.001
ON3 = ON5 = 5V
f = 300kHz
MAX1631/MAX1634
0.01 0.1
1
3.3V OUTPUT CURRENT (A)
10
200
0
0
5 10 15
SUPPLY VOLTAGE (V)
20
MAX1630/MAX1633
MAXIMUM 15V VDD OUTPUT
CURRENT vs. SUPPLY VOLTAGE
500
VDD > 13V
3.3V REGULATING
400
3.3V LOAD = 0A
300
200
PWM MODE INPUT CURRENT
vs. INPUT VOLTAGE
30
ON3 = ON5 = 5V
25
SKIP = VL
NO LOAD
20
15
10
IDLE MODE INPUT CURRENT
vs. INPUT VOLTAGE
10
ON3 = ON5 = 5V
SKIP = 0V
NO LOAD
1
0.1
100
3.3V LOAD = 3A
5
0
0
10,000
1000
5 10 15
SUPPLY VOLTAGE (V)
STANDBY INPUT CURRENT
vs. INPUT VOLTAGE
20
ON3 = ON5 = 0V
NO LOAD
100
10
1
0
5 10 15 20 25 30
INPUT VOLTAGE (V)
0
0
5 10 15 20 25
INPUT VOLTAGE (V)
SHUTDOWN INPUT CURRENT
vs. INPUT VOLTAGE
10
SHDN = 0V
8
30
6
4
2
0
0
5 10 15 20 25 30
INPUT VOLTAGE (V)
0.01
0
5 10 15 20 25 30
INPUT VOLTAGE (V)
MINIMUM VIN TO VOUT DIFFERENTIAL
vs. 5V OUTPUT CURRENT
1000
100
10
5V, 3A CIRCUIT
VOUT > 4.8V
f = 300kHz
1
0.001
0.01
0.1
1
5V OUTPUT CURRENT (A)
10
_______________________________________________________________________________________ 5
5 Page 
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
_______________Detailed Description
The MAX1630 is a dual, BiCMOS, switch-mode power-
supply controller designed primarily for buck-topology
regulators in battery-powered applications where high effi-
ciency and low quiescent supply current are critical. Light-
load efficiency is enhanced by automatic Idle Mode™
operation, a variable-frequency pulse-skipping mode that
reduces transition and gate-charge losses. Each step-
down, power-switching circuit consists of two N-channel
MOSFETs, a rectifier, and an LC output filter. The output
voltage is the average AC voltage at the switching node,
which is regulated by changing the duty cycle of the
MOSFET switches. The gate-drive signal to the N-channel
high-side MOSFET must exceed the battery voltage, and
is provided by a flying-capacitor boost circuit that uses a
100nF capacitor connected to BST_.
Devices in the MAX1630 family contain ten major circuit
blocks (Figure 2).
The two pulse-width modulation (PWM) controllers each
consist of a Dual Mode™ feedback network and multi-
plexer, a multi-input PWM comparator, high-side and
low-side gate drivers, and logic. MAX1630/MAX1631/
MAX1632 contain fault-protection circuits that monitor
the main PWM outputs for undervoltage and overvolt-
age. A power-on sequence block controls the power-
up timing of the main PWMs and determines whether
one or both of the outputs are monitored for undervolt-
age faults. The MAX1630/MAX1632/MAX1633/
MAX1635 include a secondary feedback network and
12V linear regulator to generate a 12V output from a
coupled-inductor flyback winding. The MAX1631/
MAX1634 have a secondary feedback input (SECFB)
instead, which allows a quasi-regulated, adjustable-
output, coupled-inductor flyback winding to be attached
to either the 3.3V or the 5V main inductor. Bias genera-
tor blocks include the 5V IC internal rail (VL) linear regu-
lator, 2.5V precision reference, and automatic bootstrap
switchover circuit. The PWMs share a common
200kHz/300kHz synchronizable oscillator.
These internal IC blocks aren’t powered directly from
the battery. Instead, the 5V VL linear regulator steps
down the battery voltage to supply both VL and the
gate drivers. The synchronous-switch gate drivers are
directly powered from VL, while the high-side switch
gate drivers are indirectly powered from VL via an
external diode-capacitor boost circuit. An automatic
bootstrap circuit turns off the +5V linear regulator and
powers the IC from the 5V PWM output voltage if the
output is above 4.5V.
PWM Controller Block
The two PWM controllers are nearly identical. The only
differences are fixed output settings (3.3V vs. 5V), the
VL/CSL5 bootstrap switch connected to the +5V PWM,
and SECFB. The heart of each current-mode PWM con-
troller is a multi-input, open-loop comparator that sums
three signals: the output voltage error signal with
respect to the reference voltage, the current-sense sig-
nal, and the slope compensation ramp (Figure 3). The
PWM controller is a direct-summing type, lacking a tra-
ditional error amplifier and the phase shift associated
with it. This direct-summing configuration approaches
ideal cycle-by-cycle control over the output voltage.
When SKIP = low, Idle Mode circuitry automatically
optimizes efficiency throughout the load current range.
Idle Mode dramatically improves light-load efficiency
by reducing the effective frequency, which reduces
switching losses. It keeps the peak inductor current
above 25% of the full current limit in an active cycle,
allowing subsequent cycles to be skipped. Idle Mode
transitions seamlessly to fixed-frequency PWM opera-
tion as load current increases.
With SKIP = high, the controller always operates in
fixed-frequency PWM mode for lowest noise. Each
pulse from the oscillator sets the main PWM latch that
turns on the high-side switch for a period determined
by the duty factor (approximately VOUT/VIN). As the
high-side switch turns off, the synchronous rectifier
latch sets; 60ns later, the low-side switch turns on. The
low-side switch stays on until the beginning of the next
clock cycle.
Table 3. SKIP PWM Table
SKIP
LOAD
CURRENT
MODE
Low Light
Idle
Low Heavy PWM
High
Light
PWM
High
Heavy
PWM
DESCRIPTION
Pulse-skipping, supply cur-
rent = 250µA at VIN = 12V,
discontinuous inductor
current
Constant-frequency PWM,
continuous inductor current
Constant-frequency PWM,
continuous inductor current
Constant-frequency PWM,
continuous inductor current
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet MAX1635.PDF ] | |
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