MAX1639ESE ,High-Speed Step-Down Controller with Synchronous Rectification for CPU PowerApplicationsLocal DC-DC Converters for CPUsINPUT+5VWorkstationsV VDDCCDesktop ComputersAGND BSTLAN ..
MAX1639ESE+ ,High-Speed Step-Down Controller with Synchronous Rectification for CPU PowerELECTRICAL CHARACTERISTICS(V = V = +5V, PGND = AGND = 0V, FREQ = REF, T = 0°C to +85°C, unless othe ..
MAX1639ESE+T ,High-Speed Step-Down Controller with Synchronous Rectification for CPU Powerapplications in which♦ Greater than 90% Efficiency Using N-Channeloutput voltage precision and good ..
MAX1639ESE+T ,High-Speed Step-Down Controller with Synchronous Rectification for CPU PowerApplicationsLocal DC-DC Converters for CPUsINPUT+5VWorkstationsVV DDCCDesktop ComputersAGND BSTLAN ..
MAX163BCNG ,CMOS 12-Bit A/D Converters With Track-and-HoldELECTRICAL CHARACTERISTICS
(VDD = +5V i5%, Vss = -11.4V to -15.75V, Slow Memory Mode (see text), ..
MAX163BCWG ,CMOS 12-Bit A/D Converters With Track-and-HoldFeatures
. 12-Bit Resolution
. 8.33ps Conversion Time
. Internal Analog Track-Hold
. 6MHz Full ..
MAX4385EEUK+T ,Low-Cost, 230MHz, Single/Quad Op Amps with Rail-to-Rail Outputs and ±15kV ESD ProtectionELECTRICAL CHARACTERISTICS (V = 5V, V = 0, V = V /2, V = V /2, R = ∞ to V /2, C = 2.2µF, T = T to T ..
MAX4386EESD ,Low-Cost / 230MHz / Single/Quad Op Amps with Rail-to-Rail Outputs and 15kV ESD ProtectionApplications Ultra-Small 5-Pin SOT23 and 14-Pin TSSOPSet-Top Boxes CCD Imaging PackagesSystemsSurv ..
MAX4386EEUD+T ,Low-Cost, 230MHz, Single/Quad Op Amps with Rail-to-Rail Outputs and ±15kV ESD ProtectionApplications♦ Ultra-Small 5-Pin SOT23 and 14-Pin TSSOPPackagesSet-Top Boxes CCD ImagingSystemsSurve ..
MAX4389EUT ,Ultra-Small, Low-Cost, 85MHz Op Amps with Rail-to-Rail Outputs and DisableMAX4389/MAX4390/ Ultra-Small, Low-Cost, 85MHz Op Amps withMAX4392–MAX4396 Rail-to-Rail Outputs and ..
MAX4389EUT+T ,Ultra-Small, Low-Cost, 85MHz Op Amps with Rail-to-Rail Outputs and DisableElectrical Characteristics—Single Supply(V = 5V, V = 0V, V = V /2, V = V /2, R = ∞ to V /2, DISABLE ..
MAX4390EUK ,Ultra-Small, Low-Cost, 85MHz Op Amps with Rail-to-Rail Outputs and DisableElectrical Characteristics—Single Supply (continued)(V = 5V, V = 0V, V = V /2, V = V /2, R = ∞ to V ..
MAX1639ESE
High-Speed Step-Down Controller with Synchronous Rectification for CPU Power
________________General DescriptionThe MAX1639 is an ultra-high-performance, step-down
DC-DC controller for CPU power in high-end computer
systems. Designed for demanding applications in which
output voltage precision and good transient response are
critical for proper operation, it delivers over 35A from 1.1V
to 4.5V with ±1% total accuracy from a +5V ±10% supply.
Excellent dynamic response corrects output transients
caused by the latest dynamically clocked CPUs. This
controller achieves over 90% efficiency by using synchro-
nous rectification. Flying-capacitor bootstrap circuitry
drives inexpensive, external N-channel MOSFETs.
The switching frequency is pin-selectable for 300kHz,
600kHz, or 1MHz. High switching frequencies allow the
use of a small surface-mount inductor and decrease out-
put filter capacitor requirements, reducing board area
and system cost.
Output overvoltage protection is enforced by a crowbar
circuit that turns on the low-side MOSFET with 100%
duty factor when the output is 200mV above the normal
regulation point. Other features include internal digital
soft-start, a power-good output, and a 3.5V ±1% refer-
ence output. The MAX1639 is available in a 16-pin
narrow SOIC package.
________________________ApplicationsLocal DC-DC Converters for CPUs
Workstations
Desktop Computers
LAN Servers
GTL Bus Termination
____________________________FeaturesBetter than ±1% Output Accuracy Over
Line and LoadGreater than 90% Efficiency Using N-Channel
MOSFETsPin-Selected High Switching Frequency:
300kHz, 600kHz, or 1MHzOver 35A Output CurrentResistor-Divider Adjustable Output from
1.1V to 4.5VCurrent-Mode Control for Fast Transient
Response and Cycle-by-Cycle Current-Limit
ProtectionShort-Circuit Protection with Foldback Current
LimitingCrowbar Overvoltage ProtectionPower-Good (PWROK) OutputDigital Soft-StartHigh-Current (2A) Drive Outputs
MAX1639
High-Speed Step-Down Controller with
Synchronous Rectification for CPU Power
_______________Ordering Information
Pin Configuration appears at end of data sheet.
MAX1639
High-Speed Step-Down Controller with
Synchronous Rectification for CPU Power
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VDD= VCC= +5V, PGND = AGND = 0V, FREQ = REF, TA
= 0°C to +85°C, unless otherwise noted.) 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.
VDD, VCC, PWROK to AGND....................................-0.3V to +6V
PGND to AGND..................................................................±0.3V
CSH, CSL to AGND....................................-0.3V to (VCC+ 0.3V)
DL to PGND................................................-0.3V to (VDD+ 0.3V)
REF, CC1, CC2, FREQ, FB to AGND.........-0.3V to (VCC + 0.3V)
BST to PGND..........................................................-0.3V to +12V
BST to LX..................................................................-0.3V to +6V
DH to LX.............................................(LX - 0.3V) to (BST + 0.3V)
Continuous Power Dissipation (TA= +70°C)
16-Pin Narrow SO (derate 8.70mW/°C above +70°C)....696mW
SO qJC...........................................................................65°C/W
Operating Temperature Range
MAX1639ESE....................................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
ELECTRICAL CHARACTERISTICS (continued)(VDD= VCC = +5V, PGND = AGND = 0V, FREQ = REF, TA
= 0°C to +85°C, unless otherwise noted.)
MAX1639
High-Speed Step-Down Controller with
Synchronous Rectification for CPU Power
ELECTRICAL CHARACTERISTICS (VDD= VCC= +5V, PGND = AGND = 0V, FREQ = REF, TA
= -40°C to +85°C, unless otherwise noted.) (Note 1)
Note 1:Specifications from 0°C to -40°C are guaranteed by design, not production tested.
MAX1639
High-Speed Step-Down Controller with
Synchronous Rectification for CPU Power
__________________________________________Typical Operating Characteristics(TA = +25°C, using the MAX1639 evaluation kit, unless otherwise noted.)
MAX1639
High-Speed Step-Down Controller with
Synchronous Rectification for CPU Power
______________________________________________________________Pin Description
MAX1639
High-Speed Step-Down Controller with
Synchronous Rectification for CPU PowerFigure 1. Standard Application Circuit
_______Standard Application CircuitsThe predesigned MAX1639 circuit shown in Figure 1
meets a wide range of applications with output currents
up to 35A. Use Table 1 to select components appropri-
ate for the desired output current range, and adapt the
evaluation kit PC board layout as necessary. This cir-
cuit represents a good set of trade-offs between cost,
size, and efficiency while staying within the worst-case
specification limits for stress-related parameters, such
as capacitor ripple current.
The MAX1639 circuit was designed for the specified fre-
quencies. Do not change the switching frequency with-
out first recalculating component values—particularly
the inductance, output filter capacitance, and RC1
resistance values.
___________________Detailed DescriptionThe MAX1639 is a BiCMOS power-supply controller
designed for use in switch-mode, step-down (buck)
topology DC-DC converters. Synchronous rectification
provides high efficiency. It is intended to provide the
high precision, low noise, excellent transient response,
and high efficiency required in today’s most demand-
ing applications.
MAX1639
High-Speed Step-Down Controller with
Synchronous Rectification for CPU Power
Table 1. Component List for Standard Applications
Note:Parts used in evaluation board are shown in bold.
PWM Controller Block and IntegratorThe heart of the current-mode PWM controller is a
multi-input, open-loop comparator that sums three sig-
nals (Figure 2): the buffered feedback signal, the cur-
rent-sense signal, and the slope-compensation ramp.
This direct-summing configuration approaches ideal
cycle-by-cycle control over the output voltage. The out-
put voltage error signal is generated by an error ampli-
fier that compares the amplified feedback voltage to an
internal reference.
Each pulse from the oscillator sets the main PWM latch
that turns on the high-side switch for a period deter-
mined by the duty factor (approximately VOUT/ VIN). The
current-mode feedback system regulates the peak
inductor current as a function of the output voltage error
signal. Since average inductor current is nearly the same
as peak current (assuming the inductor value is set rela-
tively high to minimize ripple current), the circuit acts as
a switch-mode transconductance amplifier. It pushes the
second output LC filter pole, normally found in a duty-
factor-controlled (voltage-mode) PWM, to a higher fre-
quency. To preserve inner-loop stability and eliminate
regenerative inductor current staircasing, a slope-
compensation ramp is summed into the main PWM com-
parator. Under fault conditions where the inductor cur-
rent exceeds the maximum current-limit threshold, the
high-side latch resets, and the high-side switch turns off.
Internal ReferenceThe internal 3.5V reference (REF) is accurate to ±1%
from 0°C to +85°C, making REF useful as a system ref-
erence. Bypass REF to AGND with a 0.1µF (min)
ceramic capacitor. A larger value (such as 2.2µF) is
recommended for high-current applications. Load reg-
ulation is 10mV for loads up to 100µA. Reference
undervoltage lockout is between 2.7V and 3V. Short-
circuit current is less than 4mA.
Synchronous-Rectifier DriverSynchronous rectification reduces conduction losses in
the rectifier by shunting the normal Schottky diode or
MOSFET body diode with a low-on-resistance MOSFET
switch. The synchronous rectifier also ensures proper
start-up by precharging the boost-charge pump used
for the high-side switch gate-drive circuit. Thus, if you
must omit the synchronous power MOSFET for cost or
other reasons, replace it with a small-signal MOSFET,
such as a 2N7002.
The DL drive waveform is simply the complement of the
DH high-side drive waveform (with typical controlled
dead time of 30ns to prevent cross-conduction or
shoot-through). The DL output’s on-resistance is 0.7Ω
(typ) and 2Ω(max).
