MAX8538EEI+ ,Dual-Synchronous Buck Controllers for Point-of-Load, Tracking, and DDR Memory Power SuppliesFeatures♦ MAX8537/MAX8539: Complete DDR SuppliesThe MAX8537/MAX8539 controllers provide a completep ..
MAX8538EEI+T ,Dual-Synchronous Buck Controllers for Point-of-Load, Tracking, and DDR Memory Power SuppliesELECTRICAL CHARACTERISTICS(V+ = 12V, EN_ = VL, BST_ = 6V, LX_ = 1V, VL load = 0mA, C = 10µF (cerami ..
MAX8538EEI+T ,Dual-Synchronous Buck Controllers for Point-of-Load, Tracking, and DDR Memory Power Suppliesfeaturesenhance flexibility. Out-of-phaseMAX8538EEI -40°C to +85°C 28 QSOPnontracking
MAX853CSA ,Low-Noise, Regulated, Negative Charge Pump Power Supplies for GaAsFET BiasMAX850–MAX85319-0238; Rev 2; 4/96Low -Noise, Regulated, Negative Charge-Pump Pow er Supplies for Ga ..
MAX853ESA ,Low-Noise / Regulated / Negative Charge-Pump Power Supplies for GaAsFET Bias
MAX853ESA ,Low-Noise / Regulated / Negative Charge-Pump Power Supplies for GaAsFET Bias
MB81N643289-60FN ,8 x 256K x 32 bit double data rate FCRAMapplications where large memory density and high effective bandwidth arerequired and where a simple ..
MB8264A-10 , MOS 65536-BIT DYNAMIC RANDOM ACCESS MEMORY
MB8264A-10 , MOS 65536-BIT DYNAMIC RANDOM ACCESS MEMORY
MB8264A-10 , MOS 65536-BIT DYNAMIC RANDOM ACCESS MEMORY
MB82D01171A-80LLPBN , 16 Mbit (1 M word x 16 bit) Mobile Phone Application Specific Memory
MB82D01171A-80LLPBN , 16 Mbit (1 M word x 16 bit) Mobile Phone Application Specific Memory
MAX8538EEI
Dual-Synchronous Buck Controllers for Point-of- Load / Tracking / and DDR Memory Power Supplies
General DescriptionThe MAX8537/MAX8539 controllers provide a complete
power-management solution for both double-data-rate
(DDR) and combiner supplies. The MAX8537 and
MAX8539 are configured for out-of-phase and in-phase
DDR power-supply operations, respectively, and gener-
ate three outputs: the main memory voltage (VDDQ), the
tracking sinking/sourcing termination voltage (VTT), and
the termination reference voltage (VTTR). The MAX8538
is configured as a dual out-of-phase controller for point-
of-load supplies. Each buck controller can source or
sink up to 25A of current, while the termination refer-
ence can supply up to 15mA output.
The MAX8537/MAX8538/MAX8539 use constant-
frequency voltage-mode architecture with operating
frequencies of 200kHz to 1.4MHz. An internal high-
bandwidth (25MHz) operational amplifier is used as an
error amplifier to regulate the output voltage. This
allows fast transient response, reducing the number of
output capacitors. An all-N-FET design optimizes effi-
ciency and cost. The MAX8537/MAX8538/MAX8539
have a 1% accurate reference. The second synchro-
nous buck controller in the MAX8537/MAX8539 and the
VTTR amplifier generate 1/2 VDDQvoltage for VTTand
VTTR, and track the VDDQwithin ±1%.
This family of controllers uses a high-side current-sense
architecture for current limiting. ILIM pins allow the set-
ting of an adjustable, lossless current limit for different
combinations of load current and RDSON. Alternately,
more accurate overcurrent limit is achieved by using
a sense resistor in series with the high-side FET.
Overvoltage protection is achieved by latching off the
high-side MOSFET and latching on the low-side MOSFET
when the output voltage exceeds 17% of its set output.
Independent enable, power-good, and soft-start features
enhance flexibility.
ApplicationsDDR Memory Power Supplies
Notebooks and Desknotes
Servers and Storage Systems
Broadband Routers
XDSL Modems and Routers
Power DSP Core Supplies
Power Combiner in Advanced VGA Cards
Networking Systems
RAMBUS Memory Power Supplies
FeaturesMAX8537/MAX8539: Complete DDR SuppliesMAX8538: Dual Nontracking ControllerOut-of-Phase (MAX8537/MAX8538) or In-Phase
(MAX8539) Operation4.5V to 23V Wide Input Range (Operate Down to
1.8V Input with External 5V Supply) Tracking Supply Maintains VTT= VTTR= 1/2 VDDQAdjustable Output from 0.8V to 3.6V with 1%
AccuracyVTTR Reference Sources and Sinks Up to 15mA200kHz to 1.4MHz Adjustable Switching
FrequencyAll-Ceramic Design Achievable>90% EfficiencyIndependent POK_ and EN_Adjustable Soft-Start and Soft-Stop for Each
OutputLossless Adjustable-Hiccup Current LimitOutput Overvoltage Protection28-Pin QSOP Package
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Supplies
Ordering Information
Pin Configurations appear at end of data sheet.
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Supplies
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 GND..............................................................-0.3V to +25V
AVL, VL to GND........................................................-0.3V to +6V
PGND to GND.......................................................-0.3V to +0.3V
FB_, EN_, POK_ to GND...........................................-0.3V to +6V
REFIN, VTTR, FREQ, SS_, COMP_ to GND....-0.3Vto (AVL + 0.3V)
BST_, ILIM_ to GND...............................................-0.3V to +30V
DH1 to LX1...............................................-0.3V to (BST1 + 0.3V)
DH2 to LX2...............................................-0.3V to (BST2 + 0.3V)
LX_ to BST_..............................................................-6V to +0.3V
LX_ to GND................................................................-2V to +25V
DL_ to PGND................................................-0.3V to (VL + 0.3V)
Continuous Power Dissipation (TA= +70°C)
28-Pin QSOP (derate 10.8mW/°C above +70°C)........860mW
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(V+ = 12V, EN_ = VL, BST_ = 6V, LX_ = 1V, VL load = 0mA, CVL= 10µF (ceramic), REFIN = 1.25V, PGND = AGND = FB_ = ILIM_ =
0V, CSS= 10nF, CVTTR= 1µF, RFREQ= 20kΩ, DH_ = open, DL_ = open, POK_ = open, circuit of Figure 1, TA
= 0°C to +85°C,unless
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Supplies
ELECTRICAL CHARACTERISTICS (continued)(V+ = 12V, EN_ = VL, BST_ = 6V, LX_ = 1V, VL load = 0mA, CVL= 10µF (ceramic), REFIN = 1.25V, PGND = AGND = FB_ = ILIM_ =
0V, CSS= 10nF, CVTTR= 1µF, RFREQ= 20kΩ, DH_ = open, DL_ = open, POK_ = open, circuit of Figure 1, TA
= 0°C to +85°C,unless
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Supplies
ELECTRICAL CHARACTERISTICS (continued)(V+ = 12V, EN_ = VL, BST_ = 6V, LX_ = 1V, VL load = 0mA, CVL= 10µF (ceramic), REFIN = 1.25V, PGND = AGND = FB_ = ILIM_ =
0V, CSS= 10nF, CVTTR= 1µF, RFREQ= 20kΩ, DH_ = open, DL_ = open, POK_ = open, circuit of Figure 1, TA
= 0°C to +85°C,unless
otherwise noted.)
ELECTRICAL CHARACTERISTICS (Note 2)(V+ = 12V, EN_ = VL, BST_ = 6V, LX_ = 1V, VL load = 0mA, CVL= 10µF (ceramic), REFIN = 1.25V, PGND = AGND = FB_ = ILIM_ =
0V, CSS= 10nF, CVTTR= 1µF, RFREQ= 20kΩ, DH_ = open, DL_ = open, POK_ = open, circuit of Figure 1, TA
= -40°C to +85°C,unless otherwise noted.)
Note 1:Operating supply range is guaranteed by the VL line-regulation test. User must short V+ to VL if a fixed 5V supply is used
(i.e., if V+ is less than 5.5V).
Note 2:Specifications to -40°C are guaranteed by design, not production tested.
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Supplies
Typical Operating Characteristics(Circuit of Figure 1, TA= +25°C, 400kHz switching frequency, VIN= 12V, unless otherwise noted.)
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Suppliesypical Operating Characteristics (continued)(Circuit of Figure 1, TA= +25°C, 400kHz switching frequency, VIN= 12V, unless otherwise noted.)
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Supplies
Pin Description
MAX8537/MAX8538/MAX8539Detailed DescriptionThe MAX8537/MAX8539 controllers provide a complete
power-management solution for both DDR and combin-
er supplies. The MAX8537 and MAX8539 are config-
ured for out-of-phase and in-phase DDR power-supply
operations, respectively. In addition to the dual-syn-
chronous buck controllers, they also contain an addi-
tional amplifier to generate a total of three outputs: the
main memory voltage (VDDQ), the tracking
sinking/sourcing termination voltage (VTT),and the ter-
mination reference voltage (VTTR). The MAX8538 is
configured as a dual out-of-phase controller for point-
of-load supplies. Each buck controller can source or
sink up to 25A of current, while the termination refer-
ence can supply up to 15mA output.
The MAX8537/MAX8539 have a 1% accurate refer-
ence. The first buck controller generates VDDQusing
external resistor-dividers. The second synchronous
buck controller and the amplifier generate 1/2 VDDQ
voltage for VTTand VTTR. The VTTand VTTRvoltages
are maintained within 1% of 1/2 VDDQ.
The MAX8537/MAX8538/MAX8539 use a constant-fre-
quency voltage-mode architecture with operating fre-
quencies of 200kHz to 1.4MHz to allow flexible design.
An internal high-bandwidth (25MHz) operational ampli-
fier is used as an error amplifier to regulate the output
voltage. This allows fast transient response, reducing
the number of output capacitors. Synchronous rectifica-
tion ensures high efficiency and balanced current
sourcing and sinking capability for VTT. An all-N-FET
design optimizes efficiency and cost. The two convert-
ers can be operated in-phase or out-of-phase to mini-
mize capacitance and optimize performance for all
VIN/VOUTcombinations.
Both channels have independent enable and power-
good functions. They also have high-side current-sense
architectures. ILIM pins allow the setting of an
adjustable, lossless current limit for different combina-
tions of load current and RDS(ON). Additionally, accu-
rate overcurrent protection is achieved by using a
sensing resistor in series with the high-side FET. The
positive current-limit threshold is programmable
through an external resistor. Overvoltage protection is
achieved by latching off the high-side MOSFET and
latching on the low-side MOSFET when the output volt-
age exceeds 17% of its set output.
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Supplies
Pin Description (continued)
DC-DC ControllerThe MAX8537/MAX8538/MAX8539 step-down DC-DC
converters use a PWM voltage-mode control scheme.
An internal high-bandwidth (25MHz) operational amplifi-
er is used as an error amplifier to regulate the output
voltage. The output voltage is sensed and compared
with an internal 0.8V reference or REFIN to generate an
error signal. The error signal is then compared with a
fixed-frequency ramp by a PWM comparator to give the
appropriate duty cycle to maintain output voltage regula-
tion. At the rising edge of the internal clock, and with DL
(the low-side MOSFET gate drive) at 0V, the high-side
MOSFET turns on. When the ramp voltage reaches the
error-amplifier output voltage, the high-side MOSFET
latches off until the next clock pulse. During the high-
side MOSFET on-time, current flows from the input,
through the inductor, and to the output capacitor and
load. At the moment the high-side MOSFET turns off,
the energy stored in the inductor during the on-time is
released to support the load as the inductor current
ramps down by commutation through the low-side
MOSFET body diode. After a fixed delay, the low-side
MOSFET turns on to shunt the current from its body
diode for lower voltage drop and increased efficiency.
The low-side MOSFET turns off at the rising edge of the
next clock pulse, and when its gate voltage discharges
to zero, the high-side MOSFET turns on and another
cycle starts.
The controllers sense peak inductor current and pro-
vide hiccup-mode overload and short-circuit protection
(see the Current Limit section).
The MAX8537/MAX8538/MAX8539 operate in forced-
PWM mode where the inductor current is always contin-
uous, so even under light load the controller maintains
a constant switching frequency to minimize noise and
possible interference with system circuitry.
Synchronous-Rectifier Driver (DL)Synchronous rectification reduces the conduction loss
in the rectifier by replacing the normal Schottky catch
diode with a low-resistance MOSFET switch. The
MAX8537/MAX8538/MAX8539 controllers also use the
synchronous rectifier to ensure proper startup of the
boost gate-drive circuit.
High-Side Gate-Drive Supply (BST)Gate-drive voltage for the high-side N-channel switch is
generated by a flying-capacitor boost circuit (Figure 1).
The capacitor between BST and LX is alternately
charged from the VL supply and placed in parallel to
the high-side MOSFET’s gate-source terminals.
On startup, the synchronous rectifier (low-side
MOSFET) forces LX to ground and charges the boost
capacitor to VL. On the second half-cycle, the switch-
mode power supply turns on the high-side MOSFET by
closing an internal switch between BST and DH. This
provides the necessary gate-to-source voltage to turn
on the high-side switch, an action that boosts the 5V
gate-drive signal above the input voltage.
Internal 5V Linear RegulatorAll MAX8537/MAX8538/MAX8539 functions are pow-
ered from the on-chip low-dropout 5V regulator with the
input connected to V+. Bypass the regulator’s output
(VL) with a 1µF/10mA or greater ceramic capacitor. The
V+ to VL dropout voltage is typically 500mV, so when
V+ is less than 5.5V, VL is typically (V+ - 500mV).
The internal linear regulator can source up to 70mA to
supply the IC, power the low-side gate drivers, and
charge the external boost capacitors. The current
required to drive the external MOSFETs is calculated as
the total gate charge of the MOSFETs at 5V multiplied
by the switching frequency. At higher frequency, the
MOSFET drive current may exceed the capability of the
internal linear regulator. The output current at VL can
be supplemented with an external PNP transistor as
shown in Figures 4 and 5, which also moves most of
the power dissipation off the IC. The external PNP can
increase the output current at VL to over 200mA. The
dropout voltage increases to 1V (typ).
Undervoltage Lockout (UVLO)If VL drops below 3.75V, the MAX8537/MAX8538/
MAX8539 assume that the supply voltage is too low to
make valid decisions, so UVLO circuitry inhibits switch-
ing and forces POK and DH low and DL high. After VL
rises above 4.3V, the controller powers up the outputs
(see the Startupsection).
StartupExternally, the MAX8537/MAX8538/MAX8539 start
switching when VL rises above the 4.3V UVLO thresh-
old. However, the controller does not start unless all
four of the following conditions are met: 1) EN_ is high,
2) VL > 4.3V, 3) the internal reference exceeds 80% of
its nominal value (VREF> 0.64V), and 4) the thermal
limit is not exceeded. Once the MAX8537/MAX8538/
MAX8539 assert the internal enable signal, the con-
troller starts switching and enables soft-start.
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Supplies
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power SuppliesFigure 1. Typical Application Circuit: MAX8537 DDR Memory Application (400kHz Switching)
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power SuppliesFigure 2. MAX8539 DDR Memory Application (400kHz Switching)
MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power SuppliesFigure 3. MAX8538 PowerPC™ Application (400kHz Switching)
