MAX1993ETG ,Quick-PWM Step-Down Controllers with Inductor Saturation Protection and Dynamic Output VoltagesMAX1992/MAX199319-2661; Rev 0; 10/02Quick-PWM Step-Down Controllers with InductorSaturation Protect ..
MAX1993ETG+ ,Quick-PWM Step-Down Controllers with Inductor Saturation Protection and Dynamic Output VoltagesMAX1992/MAX199319-2661; Rev 1; 9/05Quick-PWM Step-Down Controllers with InductorSaturation Protecti ..
MAX1993ETG+T ,Quick-PWM Step-Down Controllers with Inductor Saturation Protection and Dynamic Output VoltagesFeaturesThe MAX1992/MAX1993 pulse-width modulation (PWM)♦ Inductor Saturation Protectioncontrollers ..
MAX1993ETG+TG40 ,Quick-PWM Step-Down Controllers with Inductor Saturation Protection and Dynamic Output VoltagesFeaturesThe MAX1992/MAX1993 pulse-width modulation (PWM)♦ Inductor Saturation Protectioncontrollers ..
MAX1993ETG+TG40 ,Quick-PWM Step-Down Controllers with Inductor Saturation Protection and Dynamic Output VoltagesApplications18 17 16 15 14 13Notebook Computers VDD 19 CSN1220 11 CSPPGNDCore/IO Supplies as Low as ..
MAX1997ETJ , Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer
MAX502ACWG+T ,Voltage-Output, 12-Bit Multiplying DACsApplications
Digital Attenuators
Gain Amplifiers
Digital to 4mA-to-20mA Converters
Automatic ..
MAX502AEWG+ ,Voltage-Output, 12-Bit Multiplying DACsELECTRICAL CHARACTERISTICS
Dual Supply (VDD = +11.4V to +15.75V, Vss = -11.4V to -15.75V, VREF = ..
MAX502AEWG+T ,Voltage-Output, 12-Bit Multiplying DACsGeneral Description
The MAX501/MAX502 are 12-bit, 4-quadrant, voltage-
output, multiplying digi ..
MAX5033AASA+ ,500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC ConverterElectrical Characteristics (MAX5033_U_ _)(V = +12V, V = +12V, I = 0, T = 0°C to +85°C, unless other ..
MAX5033AUSA+ ,500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC ConverterFeaturesThe MAX5033 easy-to-use, high-efficiency, high-voltage, ● Wide 7.5V to 76V Input Voltage Ra ..
MAX5033AUSA+T ,500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC ConverterElectrical Characteristics (MAX5033_U_ _) (continued)(V = +12V, V = +12V, I = 0, T = 0°C to +85°C, ..
MAX1993ETG
Quick-PWM Step-Down Controllers with Inductor Saturation Protection and Dynamic Output Voltages
General DescriptionThe MAX1992/MAX1993 pulse-width modulation (PWM)
controllers provide high-efficiency, excellent transient
response, and high DC output accuracy. The devices
step down high-voltage batteries to generate low-
voltage CPU core or chipset/RAM supplies in notebook
computers.
Maxim’s proprietary Quick-PWM™ quick-response, con-
stant 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. Efficiency is
enhanced by the ability to drive very large synchronous-
rectifier MOSFETs. Current sensing to ensure reliable
overload and inductor saturation protection is available
using an external current-sense resistor in series with the
output. Alternatively, the controller can sense the current
across the synchronous rectifier alone or use lossless
inductor sensing for lowest power dissipation.
Single-stage buck conversion allows the MAX1992/
MAX1993 to directly step down high-voltage batteries for
the highest possible efficiency. Alternatively, two-stage
conversion (stepping down from another system supply
rail instead of the battery) at the maximum switching fre-
quency allows the minimum possible physical size.
The MAX1992 powers the CPU core, chipset, DRAM, or
other supply rails as low as 0.7V. The MAX1993 powers
chipsets and graphics processor cores, which require
dynamically adjustable output voltages. The MAX1993
provides a tracking input that can be used for active ter-
mination buses. The MAX1992/MAX1993 are available in
a 24-pin thin QFN package with optional overvoltage and
undervoltage protection.
For dual step-down PWM controllers with inductor satu-
ration protection, external reference input voltage, and
dynamically selectable output voltages, refer to the
MAX1540/MAX1541 data sheet.
ApplicationsNotebook Computers
Core/IO Supplies as Low as 0.7V
1.8V and 2.5V Supplies
DDR Memory Termination (MAX1993)
Active Termination Buses (MAX1993)
CPU/Chipset/GPU with Dynamic Voltage Cores
(MAX1993)
FeaturesInductor Saturation ProtectionAccurate Current LimitUltra-High EfficiencyQuick-PWM with 100ns Load-Step ResponseMAX1992
1.8V/2.5V Fixed or 0.7V to 5.5V Adjustable
Output RangeMAX1993
External Reference Input
Dynamically Selectable Output Voltage
(0.7V to 5.5V)
Optional Power-Good and Fault Blanking
During Transitions±1% VOUTAccuracy Over Line and Load2V to 28V Battery Input Range (VIN)200/300/450/600kHz Switching FrequencyOvervoltage/Undervoltage Protection Option1.7ms Digital Soft-StartDrives Large Synchronous Rectifier FETs2V ±0.7% Reference OutputPower-Good Window Comparator
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
Pin Configurations19-2661; Rev 0; 10/02
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
Ordering Information
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
ABSOLUTE MAXIMUM RATINGS (Note 1)
ELECTRICAL CHARACTERISTICSStresses 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............................................................-0.3V to +30V
VCCto AGND............................................................-0.3V to +6V
VDDto PGND............................................................-0.3V to +6V
PGOOD, ILIM, SKIP, SHDNto AGND......................-0.3V to +6V
REFIN, FB, CSP to AGND.........................................-0.3V to +6V
GATE, OD to GND (MAX1993 only).........................-0.3V to +6V
TON, OVP/UVP, LSAT to AGND.................-0.3V to (VCC+ 0.3V)
REF, OUT to AGND....................................-0.3V to (VCC+ 0.3V)
FBLANK to GND (MAX1993 only)..............-0.3V to (VCC+ 0.3V)
DL to PGND................................................-0.3V to (VDD+ 0.3V)
CSN to AGND............................................................-2V to +30V
DH to LX.....................................................-0.3V to (BST + 0.3V)
LX to AGND...............................................................-2V to +30V
BST to LX..................................................................-0.3V to +6V
AGND to PGND (MAX1992 only)..........................-0.3V to +0.3V
REF Short Circuit to AGND.........................................Continuous
Continuous Power Dissipation (TA= +70°C)
24-Pin 4mm x 4mm Thin QFN
(derated 20.8mW/°C above +70°C)...........................1667mW
Operating Temperature Range
MAX199_ETG..................................................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
Note 1:For the MAX1993, AGND and PGND refer to a single pin designated GND.
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
ELECTRICAL CHARACTERISTICS (continued)
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
ELECTRICAL CHARACTERISTICS (continued)
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
ELECTRICAL CHARACTERISTICS (continued)
ELECTRICAL CHARACTERISTICSDual Mode is a trademark of Maxim Integrated Products, Inc.
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
ELECTRICAL CHARACTERISTICS (continued)
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
ELECTRICAL CHARACTERISTICS (continued)
Note 2:When the inductor is in continuous conduction, the output voltage has a DC regulation level higher than the error compara-
tor threshold by 50% of the output ripple. In discontinuous conduction (SKIP= GND, light load), the output voltage has a
DC regulation level higher than the trip level by approximately 1.5% due to slope compensation.
Note 3:On-time and off-time specifications are measured from 50% point to 50% point at the DH pin with LX = GND, VBST= 5V,
and a 250pF capacitor connected from DH to LX. Actual in-circuit times can differ due to MOSFET switching speeds.
Note 4:Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics(MAX1992 Circuit of Figure1, MAX1993 Circuit of Figure9, VIN = 12V, VDD= VCC= 5V, SKIP= VCC, TON = open, TA = +25°C,
unless otherwise noted.)
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
Typical Operating Characteristics (continued)(MAX1992 Circuit of Figure 1, MAX1993 Circuit of Figure 9, VIN = 12V, VDD= VCC= 5V, SKIP= VCC, TON = open, TA = +25°C,
unless otherwise noted.)
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
Typical Operating Characteristics (continued)(MAX1992 Circuit of Figure 1, MAX1993 Circuit of Figure 9, VIN = 12V, VDD= VCC= 5V, SKIP= VCC, TON = open, TA = +25°C,
unless otherwise noted.)
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
Typical Operating Characteristics (continued)(MAX1992 Circuit of Figure 1, MAX1993 Circuit of Figure 9, VIN = 12V, VDD= VCC= 5V, SKIP= VCC, TON = open, TA = +25°C,
unless otherwise noted.)
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
Typical Operating Characteristics (continued)(MAX1992 Circuit of Figure 1, MAX1993 Circuit of Figure 9, VIN = 12V, VDD= VCC= 5V, SKIP= VCC, TON = open, TA = +25°C,
unless otherwise noted.)
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
MAX1992/MAX1993
Detailed DescriptionThe MAX1992/MAX1993 buck controllers are ideal for
low-voltage power supplies for notebook computers.
Maxim’s proprietary Quick-PWM pulse-width modulator
in the MAX1992/MAX1993 is designed for handling fast
load steps while maintaining a relatively constant oper-
ating frequency and inductor operating point over a
wide range of input voltages. The Quick-PWM architec-
ture circumvents the poor load-transient timing prob-
lems of fixed-frequency current-mode PWMs while
avoiding the problems caused by widely varying
switching frequencies in conventional constant-on-time
and constant-off-time PWM schemes.
See Table 1 for component selections and Table 2 for a
list of component suppliers.
+5V Bias Supply (VCCand VDD)The MAX1992/MAX1993 require an external 5V bias
supply in addition to the battery. Typically, this 5V bias
supply is the notebook’s 95%-efficient 5V system sup-
ply. 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 sup-
ply 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.
The 5V bias supply must provide VCC(PWM controller)
and VDD(gate-drive power), so the maximum current
drawn is:
IBIAS= ICC+ fSW(QG(LOW)+ QG(HIGH))
= 2mA to 20mA (typ)
where ICCis 550µA (typ), fSWis the switching frequency,
and QG(LOW)and QG(HIGH)are the MOSFET data
sheet’s total gate-charge specification limits at VGS= 5V.
The V+ battery input and 5V bias inputs (VCCand VDD)
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 (SHDN
going from low to high) must be delayed until the bat-
tery voltage is present in order to ensure startup.
Free-Running Constant-On-Time PWM
Controller with Input Feed ForwardThe Quick-PWM control architecture is a pseudofixed-
frequency, constant on-time, current-mode regulator
with voltage feed forward (Figure2). This architecture
relies on the output filter capacitor’s ESR to act as a
current-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 pulse width is inversely propor-
tional to input voltage and directly proportional to
output voltage. Another one-shot sets a minimum off-
time (400ns typ). The on-time one-shot is triggered if
the error comparator is low, the low-side switch current
is below the valley current-limit threshold, and the mini-
mum 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. 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 proportional to the battery
voltage as measured by the V+ input and is proportional
to the output voltage:
On-time = K (VOUT+ 0.075V) / VIN
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
Table 3. Approximate K-Factor Errors
MAX1992/MAX1993
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
MAX1992/MAX1993where K (switching period) is set by the TON pin-strap
connection (Table3), and 0.075V is an approximation to
accommodate the expected drop across the low-side
MOSFET switch. This algorithm results in a nearly con-
stant switching frequency despite the lack of a fixed-fre-
quency clock generator. The benefits of a constant
switching frequency are twofold: 1) the frequency can
be selected to avoid noise-sensitive regions such as the
455kHz IF band; 2) the inductor ripple-current operating
point remains relatively constant, resulting in easy design
methodology and predictable output voltage ripple.
The on-time one-shot has good accuracy at the operat-
ing points specified in the Electrical Characteristics
(approximately ±12.5% at 600kHz and 450kHz and
±10% at 200kHz and 300kHz). On-times at operating
points far removed from the conditions specified in the
Electrical Characteristicscan vary over a wider range.
For example, the 600kHz setting typically runs approxi-
mately 10% slower with inputs much greater than 5V
due to the very short on-times required.
The constant on-time translates only roughly to a constant
switching frequency. The on-times guaranteed in the
Electrical Characteristicsare influenced by resistive loss-
es and by switching delays in the high-side MOSFET.
Resistive losses—including the inductor, both MOSFETs,
output capacitor ESR, and PC board copper losses in the
output and ground—tend to raise the switching frequency
as the load increases. The dead-time effect increases the
effective on-time, reducing the switching frequency as
one or both dead times are added to the effective on-
time. It occurs only in PWM mode (SKIP= VCC) and
during dynamic output voltage transitions when the
inductor current reverses at light or negative load
currents. With reversed inductor current, the inductor’s
EMF causes LX to go high earlier than normal, extending
the on-time by a period equal to the DH-rising dead time.
For loads above the critical conduction point, where the
dead-time effect is no longer a factor, the actual switch-
ing frequency is:
where VDROP1is the sum of the parasitic voltage drops
in the inductor discharge path, including synchronous
rectifier, inductor, and PC board resistances; VDROP2is
the sum of the resistances in the charging path, includ-
ing the high-side switch, inductor, and PC board resis-
tances; and tONis the on-time calculated by the
MAX1992/MAX1993.
Automatic Pulse-Skipping Mode
(SKIP= GND)In skip mode (SKIP= GND), an inherent automatic
switchover to PFM takes place at light loads (Figure3).
This switchover is affected by a comparator that trun-
cates the low-side switch on-time at the inductor cur-
rent’s zero crossing. The zero-crossing comparator
differentially senses the inductor current across the cur-
rent-sense resistor (CSP to CSN). Once VCSP- VCSN
drops below 5% of the current-limit threshold (2.5mV
for the default 50mV current-limit threshold), the com-
parator forces DL low (Figure2). This mechanism caus-
es the threshold between pulse-skipping PFM and
nonskipping PWM operation to coincide with the
boundary between continuous and discontinuous
inductor-current operation (also known as the critical
conduction point). The load-current level at which
PFM/PWM crossover occurs, ILOAD(SKIP), is equal to
one-half the peak-to-peak ripple current, which is a
function of the inductor value (Figure3). This threshold
is relatively constant, with only a minor dependence on
battery voltage:
where K is the on-time scale factor (Table3). For exam-
ple, in the standard application circuit (K = 3.3µs, VOUT=
2.5V, VIN= 12V, and L = 4.3µH), the pulse-skipping
switchover occurs at:
The crossover point occurs at an even lower value if a
swinging (soft-saturation) inductor is used. The switch-
ing waveforms can appear noisy and asynchronous
when light loading causes pulse-skipping operation,
but this is a normal operating condition that results in
high light-load efficiency. Trade-offs in PFM noise vs.
light-load efficiency are made by varying the inductor
value. Generally, low inductor values produce a broad-
er efficiency vs. load curve, while higher values result in
higher full-load efficiency (assuming that the coil resis-
tance remains fixed) and less output voltage ripple.
Penalties for using higher inductor values include larger
physical size and degraded load-transient response
(especially at low input voltage levels).
Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
