MAX1632CAI ,Multi-Output / Low-Noise Power-Supply Controllers for Notebook Computersfeatures.+5V (RTC) +12V____
MAX1632CAI ,Multi-Output / Low-Noise Power-Supply Controllers for Notebook ComputersMAX1630–MAX163519-0480; Rev 3; 4/97Multi-Output, Low-Noise Power-SupplyControllers for Notebook Com ..
MAX1632CAI ,Multi-Output / Low-Noise Power-Supply Controllers for Notebook ComputersMAX1630–MAX163519-0480; Rev 3; 4/97Multi-Output, Low-Noise Power-SupplyControllers for Notebook Com ..
MAX1632EAI ,Multi-Output / Low-Noise Power-Supply Controllers for Notebook ComputersMAX1630–MAX163519-0480; Rev 3; 4/97Multi-Output, Low-Noise Power-SupplyControllers for Notebook Com ..
MAX1632EAI. ,Multi-Output / Low-Noise Power-Supply Controllers for Notebook ComputersMAX1630–MAX163519-0480; Rev 3; 4/97Multi-Output, Low-Noise Power-SupplyControllers for Notebook Com ..
MAX1632EAI+ ,Multi Output, Low-Noise Power Supply Controllers for Notebook ComputersFeatures♦ 96% Efficiency The MAX1630–MAX1635 are buck-topology, step-down,switch-mode, power-supply ..
MAX4376FAUK ,Single/Dual/Quad High-Side Current-Sense Amplifiers with Internal GainApplicationsTOP VIEW+Notebook Computers Portable/Battery-PoweredOUT1 5 RS-SystemsCurrent-Limited Po ..
MAX4376FAUK+T ,Single/Dual/Quad High-Side Current-Sense Amplifiers with Internal GainFeaturesThe MAX4376/MAX4377/MAX4378 single, dual, and ♦ Low-Cost, Single/Dual/Quad, High-Side Curre ..
MAX4376FAUK-T ,Single/Dual/Quad High-Side Current-Sense Amplifiers with Internal GainApplicationsOUT15 RS-Notebook Computers Portable/Battery-PoweredSystemsMAX4376Current-Limited Power ..
MAX4376HAUK/V+T ,Single/Dual/Quad High-Side Current-Sense Amplifiers with Internal GainApplicationsTOP VIEW+Notebook Computers Portable/Battery-PoweredOUT1 5 RS-SystemsCurrent-Limited Po ..
MAX4376HAUK+ ,Single/Dual/Quad High-Side Current-Sense Amplifiers with Internal GainELECTRICAL CHARACTERISTICS(V = 0 to 28V, V = (V - V ) = 0V, V = +3.0V to +28V, R = ∞, T = T to T un ..
MAX4376HAUK+T ,Single/Dual/Quad High-Side Current-Sense Amplifiers with Internal Gain MAX4376/MAX4377/MAX4378Single/Dual/Quad, High-Side Current-SenseAmplifiers with Internal Gain
MAX1630CAI-MAX1630EAI-MAX1631CAI-MAX1631EAI-MAX1632CAI-MAX1632EAI-MAX1632EAI.-MAX1633EAI-MAX1634CAI-MAX1634EAI-MAX1634EAI.-MAX1635CAI-MAX1635EAI
Multi-Output / Low-Noise Power-Supply Controllers for Notebook Computers
________________General DescriptionThe 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 SKIPpin 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.
________________________ApplicationsNotebook and Subnotebook Computers
PDAs and Mobile Communicators
Desktop CPU Local DC-DC Converters
____________________________Features96% Efficiency +4.2V to +30V Input Range 2.5V to 5.5V Dual Adjustable OutputsSelectable 3.3V and 5V Fixed or Adjustable
Outputs (Dual Mode™)12V Linear Regulator Adjustable Secondary Feedback
(MAX1631/MAX1634)5V/50mA Linear Regulator OutputPrecision 2.5V Reference OutputProgrammable Power-Up SequencingPower-Good (RESET) OutputOutput Overvoltage Protection
(MAX1630/MAX1631/MAX1632)Output Undervoltage Shutdown
(MAX1630/MAX1631/MAX1632)200kHz/300kHz Low-Noise, Fixed-Frequency
OperationLow-Dropout, 99% Duty-Factor Operation 2.5mW Typical Quiescent Power (+12V input, both
SMPSs on)4µA Typical Shutdown Current28-Pin SSOP Package
MAX1630–MAX1635
Controllers for Notebook Computers
________________Functional Diagram
_______________Ordering InformationIdle Mode and Dual Mode are trademarks of Maxim Integrated
Products.
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(V+ = 15V, both PWMs on, SYNC = VL, VL load = 0mA, REF load = 0mA, SKIP= 0V, TA= TMINto TMAX, unless otherwise noted.
Typical values are at TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
V+ to GND..............................................................-0.3V to +36V
PGND to GND.....................................................................±0.3V
VL to GND................................................................-0.3V to +6V
BST3, BST5 to GND...............................................-0.3V to +36V
LX3 to BST3..............................................................-6V to +0.3V
LX5 to BST5..............................................................-6V to +0.3V
REF, SYNC, SEQ, STEER, SKIP, TIME/ON5,
SECFB, RESETto GND............................................-0.3V to +6V
VDDto GND............................................................-0.3V to +20V
RUN/ON3, SHDNto GND.............................-0.3V to (V+ + 0.3V)
12OUT to GND...........................................-0.3V to (VDD+ 0.3V)
DL3, DL5 to PGND........................................-0.3V to (VL + 0.3V)
DH3 to LX3...............................................-0.3V to (BST3 + 0.3V)
DH5 to LX5...............................................-0.3V to (BST5 + 0.3V)
VL, REF Short to GND................................................Momentary
12OUT Short to GND..................................................Continuous
REF Current...........................................................+5mA to -1mA
VL Current.........................................................................+50mA
12OUT Current...............................................................+200mA
VDDShunt Current............................................................+15mA
Operating Temperature Ranges
MAX163_CAI.......................................................0°C to +70°C
MAX163_EAI....................................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Continuous Power Dissipation (TA= +70°C)
SSOP (derate 9.52mW/°C above +70°C)....................762mW
Lead Temperature (soldering, 10sec).............................+300°C
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)(V+ = 15V, both PWMs on, SYNC = VL, VL load = 0mA, REF load = 0mA, SKIP= 0V, TA= TMINto TMAX, unless otherwise noted.
Typical values are at TA= +25°C.)
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
Note 1:Each of the four digital soft-start levels is tested for functionality; the steps are typically in 20mV increments.
Note 2:High duty-factor operation supports low input-to-output differential voltages, and is achieved at a lowered operating
frequency (see Overload and Dropout Operationsection).
Note 3:MAX1630/MAX1632/MAX1633/MAX1635 only.
Note 4:Off mode for the 12V linear regulator occurs when the SMPS that has flyback feedback (VDD) steered to it is disabled. In
situations where the main outputs are being held up by external keep-alive supplies, turning off the 12OUT regulator pre-
vents a leakage path from the output-referred flyback winding, through the rectifier, and into VDD.
Note 5:Since the reference uses VL as its supply, the reference’s V+ line-regulation error is insignificant.
ELECTRICAL CHARACTERISTICS (continued)(V+ = 15V, both PWMs on, SYNC = VL, VL load = 0mA, REF load = 0mA, SKIP= 0V, TA= TMINto TMAX, unless otherwise noted.
Typical values are at TA= +25°C.)
MAX1630–MAX1635
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.)
__________________________________________________________________________Pin Description
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
____________________________________Typical Operating Characteristics (continued)(Circuit of Figure 1, 3A Table 1 components, TA = +25°C, unless otherwise noted.)
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
_________________________________________________Pin Description (continued)
_______Standard Application CircuitThe basic MAX1631/MAX1634 dual-output 3.3V/5V
buck converter (Figure 1) is easily adapted to meet a
wide range of applications with inputs up to 28V by
substituting components from Table 1. These circuits
represent a good set of tradeoffs between cost, size,
and efficiency, while staying within the worst-case
specification limits for stress-related parameters, such
as capacitor ripple current. Don’t change the frequency
of these circuits without first recalculating component
values (particularly inductance value at maximum bat-
tery voltage). Adding a Schottky rectifier across each
synchronous rectifier improves the efficiency of these
circuits by approximately 1%, but this rectifier is other-
wise not needed because the MOSFETs required for
these circuits typically incorporate a high-speed silicon
diode from drain to source. Use a Schottky rectifier
rated at a DC current equal to at least one-third of the
load current.
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook ComputersFigure 1. Standard 3.3V/5V Application Circuit (MAX1631/MAX1634)
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
Table 1. Component Selection for Standard 3.3V/5V Application
Table 2. Component Suppliers*Distributor
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook ComputersFigure 2. MAX1632 Block Diagram
_______________Detailed DescriptionThe 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 BlockThe 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.
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook ComputersFigure 3. PWM Controller Detailed Block Diagram
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook ComputersFigure 4. Main PWM Comparator Block Diagram
In PWM mode, the controller operates as a fixed-
frequency current-mode controller where the duty ratio
is set by the input/output voltage ratio. The current-
mode feedback system regulates the peak inductor
current value as a function of the output-voltage error
signal. In continuous-conduction mode, the average
inductor current is nearly the same as the peak current,
so the circuit acts as a switch-mode transconductance
amplifier. This pushes the second output LC filter pole,
normally found in a duty-factor-controlled (voltage-
mode) PWM, to a higher frequency. To preserve inner-
loop stability and eliminate regenerative inductor
current “staircasing,” a slope compensation ramp is
summed into the main PWM comparator to make the
apparent duty factor less than 50%.
The MAX1630 family uses a relatively low loop gain,
allowing the use of lower-cost output capacitors. The
relative gains of the voltage-sense and current-sense
inputs are weighted by the values of current sources
that bias three differential input stages in the main PWM
comparator (Figure 4). The relative gain of the voltage
comparator to the current comparator is internally fixed
at K = 2:1. The low loop gain results in the 2% typical
load-regulation error. The low value of loop gain helps
reduce output filter capacitor size and cost by shifting
the unity-gain crossover frequency to a lower level.
The output filter capacitors (Figure 1, C1 and C2) set a
dominant pole in the feedback loop that must roll off the
loop gain to unity before encountering the zero intro-
duced by the output capacitor’s parasitic resistance
(ESR) (see Design Proceduresection). A 60kHz pole-
zero cancellation filter provides additional rolloff above
the unity-gain crossover. This internal 60kHz lowpass
compensation filter cancels the zero due to filter capaci-
tor ESR. The 60kHz filter is included in the loop in both
fixed-output and adjustable-output modes.
Synchronous Rectifier Driver (DL) Synchronous rectification reduces conduction losses in
the rectifier by shunting the normal Schottky catch diode
with a low-resistance MOSFET switch. Also, the synchro-
nous rectifier ensures proper start-up of the boost gate-
driver circuit. If the synchronous power MOSFETs are
omitted for cost or other reasons, replace them with a
small-signal MOSFET, such as a 2N7002.
If the circuit is operating in continuous-conduction
mode, the DL drive waveform is simply the complement
of the DH high-side drive waveform (with controlled
dead time to prevent cross-conduction or “shoot-
through”). In discontinuous (light-load) mode, the syn-
chronous switch is turned off as the inductor current
falls through zero. The synchronous rectifier works
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computersunder all operating conditions, including Idle Mode.
The SECFB signal further controls the synchronous
switch timing in order to improve multiple-output cross-
regulation (see Secondary Feedback Regulation Loop
section).
Internal VL and REF SuppliesAn internal regulator produces the +5V supply (VL) that
powers the PWM controller, logic, reference, and other
blocks within the IC. This 5V low-dropout linear regula-
tor supplies up to 25mA for external loads, with a
reserve of 25mA for supplying gate-drive power.
Bypass VL to GND with 4.7µF.
Important:Ensure that VL does not exceed 6V.
Measure VL with the main output fully loaded. If it is
pumped above 5.5V, either excessive boost diode
capacitance or excessive ripple at V+ is the probable
cause. Use only small-signal diodes for the boost cir-
cuit (10mA to 100mA Schottky or 1N4148 are pre-
ferred), and bypass V+ to PGND with 4.7µF directly at
the package pins.
The 2.5V reference (REF) is accurate to ±2% over tem-
perature, making REF useful as a precision system ref-
erence. Bypass REF to GND with 1µF minimum. REF
can supply up to 5mA for external loads. (Bypass REF
with a minimum 1µF/mA reference load current.)
However, if extremely accurate specifications for both
the main output voltages and REF are essential, avoid
loading REF more than 100µA. Loading REF reduces
the main output voltage slightly, because of the refer-
ence load-regulation error.
When the 5V main output voltage is above 4.5V, an
internal P-channel MOSFET switch connects CSL5 to
VL, while simultaneously shutting down the VL linear
regulator. This action bootstraps the IC, powering the
internal circuitry from the output voltage, rather than
through a linear regulator from the battery.
Bootstrapping reduces power dissipation due to gate
charge and quiescent losses by providing that power
from a 90%-efficient switch-mode source, rather than
from a much less efficient linear regulator.
Boost High-Side Gate-Drive Supply
(BST3 and BST5) Gate-drive voltage for the high-side N-channel switches
is generated by a flying-capacitor boost circuit
(Figure 2). The capacitor between BST_ and LX_ is
alternately charged from the VL supply and placed par-
allel to the high-side MOSFET’s gate-source terminals.
On start-up, the synchronous rectifier (low-side
MOSFET) forces LX_ to 0V and charges the boost
capacitors to 5V. On the second half-cycle, the SMPS
turns on the high-side MOSFET by closing an internal
switch between BST_ and DH_. This provides the nec-
essary enhancement voltage to turn on the high-side
switch, an action that “boosts” the 5V gate-drive signal
above the battery voltage.
Ringing at the high-side MOSFET gate (DH3 and DH5)
in discontinuous-conduction mode (light loads) is a nat-
ural operating condition. It is caused by residual ener-
gy in the tank circuit, formed by the inductor and stray
capacitance at the switching node, LX. The gate-drive
negative rail is referred to LX, so any ringing there is
directly coupled to the gate-drive output.
Current-Limiting and Current-Sense
Inputs (CSH and CSL)The current-limit circuit resets the main PWM latch and
turns off the high-side MOSFET switch whenever the
voltage difference between CSH and CSL exceeds
100mV. This limiting is effective for both current flow
directions, putting the threshold limit at ±100mV. The
tolerance on the positive current limit is ±20%, so the
external low-value sense resistor (R1) must be sized for
80mV/IPEAK, where IPEAKis the required peak inductor
current to support the full load current, while compo-
nents must be designed to withstand continuous cur-
rent stresses of 120mV/R1.
For breadboarding or for very-high-current applications,
it may be useful to wire the current-sense inputs with a
twisted pair, rather than PC traces. (This twisted pair
needn’t be anything special; two pieces of wire-wrap
wire twisted together are sufficient.) This reduces the
possible noise picked up at CSH_ and CSL_, which can
cause unstable switching and reduced output current.
The CSL5 input also serves as the IC’s bootstrap sup-
ply input. Whenever VCSL5> 4.5V, an internal switch
connects CSL5 to VL.
Oscillator Frequency and
Synchronization (SYNC)The SYNC input controls the oscillator frequency. Low
selects 200kHz; high selects 300kHz. SYNC can also
be used to synchronize with an external 5V CMOS or
TTL clock generator. SYNC has a guaranteed 240kHz
to 350kHz capture range. A high-to-low transition on
SYNC initiates a new cycle.
300kHz operation optimizes the application circuit for
component size and cost. 200kHz operation provides
increased efficiency, lower dropout, and improved
load-transient response at low input-output voltage dif-
ferences (see Low-Voltage Operationsection).
