MAX1715EEI ,Ultra-High Efficiency / Dual Step-Down Controller for Notebook ComputersMAX171519-1541; Rev 0; 1/00Ultra-High Efficiency, Dual Step-DownController for Notebook Computers
MAX1715EEI+ ,Ultra-High-Efficiency, Dual Step-Down Controller for Notebook ComputersFeaturesThe MAX1715 PWM controller provides the high effi-♦ Ultra-High Efficiencyciency, excellent ..
MAX1715EEI+T ,Ultra-High-Efficiency, Dual Step-Down Controller for Notebook ComputersELECTRICAL CHARACTERISTICS(Circuit of Figure 1, 4A components from Table 1, V V = +5V, SKIP = AGND, ..
MAX1717 ,Dynamically Adjustable, Synchronous Step-Down Controller for Notebook CPUsApplicationsinput/output voltage ratios with ease and provides100ns “instant-on” response to load t ..
MAX1717EEG ,Dynamically Adjustable / Synchronous Step-Down Controller for Notebook CPUsApplications100ns “instant-on” response to load transients while 2V to 28V Battery Input Range mai ..
MAX1717EEG ,Dynamically Adjustable / Synchronous Step-Down Controller for Notebook CPUsELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V+ = +15V, V = V = SKP/SDN = +5V, V = 1.6V, T = 0°C ..
MAX4544CUA ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesFeaturesThe MAX4541–MAX4544 are precision, dual analog Low R : 60Ω max (33Ω typ)ONswitches design ..
MAX4544CUA+ ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesGeneral Description ________
MAX4544EPA ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesGeneral Description ________
MAX4544ESA ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesELECTRICAL CHARACTERISTICS—Single +5V Supply(V+ = +5V ±10%, GND = 0, V = 2.4V, V = 0.8V, T = T to T ..
MAX4544ESA ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesFeaturesThe MAX4541–MAX4544 are precision, dual analog Low R : 60Ω max (33Ω typ)ONswitches design ..
MAX4544ESA ,Low-Voltage, Single-Supply Dual SPST/SPDT Analog SwitchesGeneral Description ________
MAX1715EEI
Ultra-High Efficiency / Dual Step-Down Controller for Notebook Computers
General DescriptionThe MAX1715 PWM controller provides the high effi-
ciency, excellent transient response, and high DC out-
put accuracy needed for stepping down high-voltage
batteries to generate low-voltage CPU core, I/O, and
chipset RAM supplies in notebook computers.
Maxim’s proprietary Quick-PWM™ quick-response,
constant-on-time PWM control scheme handles wide
input/output voltage ratios with ease and provides
100ns “instant-on” response to load transients while
maintaining a relatively constant switching frequency.
The MAX1715 achieves high efficiency at a reduced
cost by eliminating the current-sense resistor found in
traditional current-mode PWMs. Efficiency is further
enhanced by its ability to drive very large synchronous-
rectifier MOSFETs.
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 MAX1715 is intended for CPU core, chipset,
DRAM, or other low-voltage supplies as low as 1V. The
MAX1715 is available in a 28-pin QSOP package. For
applications requiring VID compliance or DAC control
of output voltage, refer to the MAX1710/MAX1711 data
sheet. For a single-output version, refer to the MAX1714
data sheet.
ApplicationsNotebook Computers
CPU Core Supply
Chipset/RAM Supply as Low as 1V
1.8V and 2.5V I/O Supply
FeaturesUltra-High EfficiencyNo Current-Sense Resistor (lossless ILIMIT)Quick-PWM with 100ns Load-Step Response1% VOUTAccuracy over Line and LoadDual-Mode Fixed 1.8V/3.3V/Adj or 2.5V/Adj OutputsAdjustable 1V to 5.5V Output Range2V to 28V Battery Input Range200/300/420/540kHz Nominal Switching FrequencyOver/Undervoltage Protection1.7ms Digital Soft-StartDrives Large Synchronous-Rectifier FETsPower-Good Indicator
MAX1715, Dual Step-Down
Controller for Notebook ComputersQuick-PWM is a trademark of Maxim Integrated Products.
Ordering Information
Minimal Operating Circuit
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computers
ABSOLUTE MAXIMUM RATINGSStresses 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 AGND..............................................................-0.3 to +30V
VDD, VCCto AGND..................................................-0.3V to +6V
PGND to AGND or VCCto VDD...........................................±0.3V
PGOOD, OUT_ to AGND..........................................-0.3V to +6V
ILIM_, FB_, REF, SKIP, TON,
ON_ to AGND...........................................-0.3V to (VDD+ 0.3V)
DL_ to PGND..............................................-0.3V to (VDD+ 0.3V)
BST_ to AGND........................................................-0.3V to +36V
DH1 to LX1...............................................-0.3V to (BST1 + 0.3V)
DH2 to LX2...............................................-0.3V to (BST2 + 0.3V)
LX1 to BST1..............................................................-6V to +0.3V
LX2 to BST2..............................................................-6V to +0.3V
REF Short Circuit to AGND.........................................Continuous
Continuous Power Dissipation (TA= +70°C)
28-Pin QSOP (derate 8.0mW/°C above +70°C).....640mW/°C
Operating Temperature Range ..........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range ............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, 4A components from Table 1, VCC = VDD= +5V, SKIP= AGND, V+ = 15V, TA
= 0°C to +85°C, unless otherwisenoted.) (Note 1)
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, 4A components from Table 1, VCC = VDD= +5V, SKIP= AGND, V+ = 15V, TA
= 0°C to +85°C, unless otherwisenoted.) (Note 1)
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computers
ELECTRICAL CHARACTERISTICS (Circuit of Figure 1, 4A components from Table 1, VCC = VDD= +5V, SKIP= AGND, V+ = 15V, TA
= -40°C to +85°C, unless otherwisenoted.) (Note 1)
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, 4A components from Table 1, VCC = VDD= +5V, SKIP= AGND, V+ = 15V, TA
= 0°C to +85°C, unless otherwisenoted.) (Note 1)
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook ComputersMAX1715-01
LOAD CURRENT (A)
EFFICIENCY (%)
EFFICIENCY vs. LOAD CURRENT
(1.8V, 4A COMPONENTS, SKIP = GND)MAX1715-02
LOAD CURRENT (A)
EFFICIENCY (%)
EFFICIENCY vs. LOAD CURRENT
(1.8V, 4A COMPONENTS, SKIP = VCC)MAX1715-03
LOAD CURRENT (A)
EFFICIENCY (%)
EFFICIENCY vs. LOAD CURRENT
(2.5V, 4A COMPONENTS, SKIP = GND)
Note 1:Specifications to -40°C are guaranteed by design, and not production tested.
Note 2:When the inductor is in continuous conduction, the output voltage will have a DC regulation higher than the trip level by
50% of the ripple. In discontinuous conduction (SKIP= AGND, light load) the output voltage will have DC regulation
higher than the trip level by approximately 1.5% due to slope compensation.
Note 3:On-time and off-time specifications are measured from the 50% point at the DH pin with LX = PGND, VBST= 5V. Actual
in-circuit times may differ due to MOSFET switching speeds.
__________________________________________Typical Operating Characteristics(Circuit of Figure 1, components from Table 1, VIN= +15V, SKIP= AGND, TON= unconnected, TA= +25°C, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, 4A components from Table 1, VCC = VDD= +5V, SKIP= AGND, V+ = 15V, TA
= -40°C to +85°C, unless otherwisenoted.) (Note 1)
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computers
_____________________________Typical Operating Characteristics (continued)(Circuit of Figure 1, components from Table 1, VIN= +15V, SKIP= AGND, TON= unconnected, TA= +25°C, unless otherwise noted.)
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computers
_____________________________Typical Operating Characteristics (continued)= +25°C, unless otherwise noted.)
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computers
Pin Description
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computers
Pin Description (continued)
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook ComputersFigure 1. Standard Application Circuit
Standard Application CircuitThe standard application circuit (Figure 1) generates
two low-voltage rails for general-purpose use in note-
book computers (I/O supply, fixed CPU core supply,
DRAM supply). This DC-DC converter steps down a
battery or AC adapter voltage to voltages from 1.0V to
5.5V with high efficiency and accuracy.
See Table 1 for a list of components for common appli-
cations. Table 2 lists component manufacturers.
Detailed DescriptionThe MAX1715 buck controller is designed for low-volt-
age power supplies for notebook computers. Maxim’s
proprietary Quick-PWM pulse-width modulator in the
MAX1715 (Figure 2) is specifically designed for han-
dling fast load steps while maintaining a relatively con-
stant operating frequency and inductor operating point
over a wide range of input voltages. The Quick-PWM
architecture circumvents the poor load-transient timing
problems of fixed-frequency current-mode PWMs while
also avoiding the problems caused by widely varying
switching frequencies in conventional constant-on-time
and constant-off-time PWM schemes.
+5V Bias Supply (VCCand VDD)The MAX1715 requires an external +5V bias supply in
addition to the battery. Typically, this +5V bias supply
is the notebook’s 95% efficient +5V system supply.
Keeping the bias supply external to the IC improves
efficiency and eliminates the cost associated with the
+5V linear regulator that would otherwise be needed to
supply the PWM circuit and gate drivers. If stand-alone
capability is needed, the +5V supply can be generated
with an external linear regulator such as the MAX1615.
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook ComputersThe power input and +5V bias inputs can be connected
together if the input source is a fixed +4.5V to +5.5V
supply. If the +5V bias supply is powered up prior to
the battery supply, the enable signal (ON1, ON2) must
be delayed until the battery voltage is present to ensure
start-up. The +5V bias supply must provide VCCand
gate-drive power, so the maximum current drawn is:
IBIAS= ICC+ f (QG1 + QG2) = 5mA to 30mA (typ)
where ICC is 1mA typical, f is the switching frequency,
and QG1 and QG2 are the MOSFET data sheet total
gate-charge specification limits at VGS= 5V.
Free-Running, Constant-On-Time PWM
Controller with Input Feed-ForwardThe Quick-PWM control architecture is a pseudo-fixed-
frequency, constant-on-time current-mode type with
voltage feed-forward (Figure 3). This architecture relies
on the output filter capacitor’s ESR to act as the cur-
rent-sense resistor, so the output ripple voltage pro-
vides the PWM ramp signal. The control algorithm is
simple: the high-side switch on-time is determined sole-
ly by a one-shot whose period is inversely proportional
to input voltage and directly proportional to output volt-
age. Another one-shot sets a minimum off-time (400ns
typ). The on-time one-shot is triggered if the error com-
parator is low, the low-side switch current is below the
Table 1. Component Selection for Standard Applications
Table 2. Component Suppliers
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computerscurrent-limit threshold, and the minimum off-time one-
shot has timed out.
On-Time One-Shot (TON)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 lack of a fixed-frequency clock generator.
The benefits of a constant switching frequency are
twofold: first, the frequency can be selected to avoid
noise-sensitive regions such as the 455kHz IF band;
second, the inductor ripple-current operating point
remains relatively constant, resulting in easy design
methodology and predictable output voltage ripple.
The on-times for side 1 are set 15% higher than the
Figure 2. Functional Diagram
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook ComputersFigure 3. PWM Controller (one side only)
X = Don’t care
Table 3. Operating Mode Truth Table
MAX1715
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computersnominal frequency setting (200kHz, 300kHz, 420kHz, or
540kHz), while the on-times for side 2 are set 15%
lower than nominal. This is done to prevent audio-fre-
quency “beating” between the two sides, which switch
asynchronously for each side:
On-Time = K (VOUT+ 0.075V) / VIN
where K is set by the TON pin-strap connection and
0.075V is an approximation to accommodate for the
expected drop across the low-side MOSFET switch.
One-shot timing error increases for the shorter on-time
settings due to fixed propagation delays; it is approxi-
mately ±12.5% at 540kHz and 420kHz nominal settings
and ±10% at the two slower settings. This translates to
reduced switching-frequency accuracy at higher fre-
quencies (Table 5). Switching frequency increases as a
function of load current due to the increasing drop
across the low-side MOSFET, which causes a faster
inductor-current discharge ramp. The on-times guaran-
teed in the Electrical Characteristicsare influenced by
switching delays in the external high-side power MOS-
FET.
Two external factors that influence switching-frequency
accuracy are resistive drops in the two conduction
loops (including inductor and PC board resistance) and
the dead-time effect. These effects are the largest con-
tributors to the change of frequency with changing load
current. The dead-time effect increases the effective
on-time, reducing the switching frequency as one or
both dead times. It occurs only in PWM mode (SKIP=
high) when the inductor current reverses at light or neg-
ative load currents. With reversed inductor current, the
inductor’s EMF causes LX to go high earlier than nor-
mal, extending the on-time by a period equal to the
low-to-high dead time.
For loads above the critical conduction point, the actual
switching frequency is:
where VDROP1 is the sum of the parasitic voltage drops
in the inductor discharge path, including synchronous
rectifier, inductor, and PC board resistances; VDROP2
is the sum of the resistances in the charging path; and
tONis the on-time calculated by the MAX1715.
Automatic Pulse-Skipping SwitchoverIn skip mode (SKIPlow), an inherent automatic
switchover to PFM takes place at light loads. This
switchover is effected by a comparator that truncates
the low-side switch on-time at the inductor current’s
zero crossing. This mechanism causes the threshold
between pulse-skipping PFM and nonskipping PWM
operation to coincide with the boundary between con-
tinuous and discontinuous inductor-current operation
(also known as the “critical conduction” point). For a
battery range of 7V to 24V, this threshold is relatively
constant, with only a minor dependence on battery volt-
age.
where K is the on-time scale factor (Table 5). The load-
current level at which PFM/PWM crossover occurs,
ILOAD(SKIP), is equal to 1/2 the peak-to-peak ripple cur-
rent, which is a function of the inductor value (Figure 4).
For example, in the standard application circuit with
VOUT1= 2.5V, VIN= 15V, and K = 2.96µs (see Table
5), switchover to pulse-skipping operation occurs at
ILOAD= 0.7A or about 1/6 full load. The crossover point
occurs at an even lower value if a swinging (soft-satura-
tion) inductor is used.
The switching waveforms may appear noisy and asyn-
chronous when light loading causes pulse-skipping
Table 4. Frequency Selection Guidelines
