MAX1954AEUB+ Fast Delivery |IC PHOENIX CO.,LIMITED

MAX1954AEUB+ ,Low-Cost, Current-Mode PWM Buck Controller with Foldback Current LimitApplicationsOrdering InformationPrinters and Scanners PART TEMP RANGE PIN-PACKAGEGraphic Cards and ..
MAX1954EUB ,Low-Cost / High-Frequency / Current-Mode PWM Buck ControllerELECTRICAL CHARACTERISTICS(V = 5V, V - V = 5V, T = -40°C to +85°C, unless otherwise noted. Typical ..
MAX1954EUB ,Low-Cost / High-Frequency / Current-Mode PWM Buck ControllerELECTRICAL CHARACTERISTICS (continued)(V = 5V, V - V = 5V, T = -40°C to +85°C, unless otherwise not ..
MAX1954EUB ,Low-Cost / High-Frequency / Current-Mode PWM Buck ControllerELECTRICAL CHARACTERISTICS (continued)(V = 5V, V - V = 5V, T = -40°C to +85°C, unless otherwise not ..
MAX1954EUB+ ,Low-Cost, High-Frequency, Current-Mode PWM Buck ControllersApplicationsPrinters and ScannersILIM 1 10 BSTGraphic Cards and Video CardsCOMP 2 9 LXPCs and Serve ..
MAX1954EUB+ ,Low-Cost, High-Frequency, Current-Mode PWM Buck ControllersApplicationsPrinters and ScannersILIM 1 10 BSTGraphic Cards and Video CardsCOMP 2 9 LXPCs and Serve ..
MAX490MJA ,Low-Power / Slew-Rate-Limited RS-485/RS-422 TransceiversMAX481/MAX483/MAX485/MAX487–MAX491/MAX148719-0122; Rev 5; 2/96Low-Power, Slew-Rate-LimitedRS-485/RS ..
MAX491 ,Low-Power, Slew-Rate-Limited RS-485/RS-422 TransceiversApplicationsIndustrial-Control Local Area Networks Ordering Information appears at end of data shee ..
MAX491CPD ,Low-Power / Slew-Rate-Limited RS-485/RS-422 TransceiversGeneral Description ________
MAX491CPD+ ,Low-Power, Slew-Rate-Limited RS-485/RS-422 TransceiversApplicationsMAX3483E/MAX3485E/MAX3486E/MAX3488E/Low-Power RS-485 TransceiversMAX3490E/MAX3491E: +3. ..
MAX491CSD ,Low-Power / Slew-Rate-Limited RS-485/RS-422 TransceiversApplications ______________Ordering InformationLow-Power RS-485 TransceiversPART TEMP. RANGE PIN-PA ..
MAX491CSD ,Low-Power / Slew-Rate-Limited RS-485/RS-422 TransceiversMAX481/MAX483/MAX485/MAX487–MAX491/MAX148719-0122; Rev 5; 2/96Low-Power, Slew-Rate-LimitedRS-485/RS ..

MAX1954AEUB+
Low-Cost, Current-Mode PWM Buck Controller with Foldback Current Limit
General Description
The MAX1954A synchronous current-mode, pulse-
width modulation (PWM) buck controller is pin compati-
ble with the popular MAX1954 and is suitable for
applications where cost and size are critical.
The MAX1954A operates from an input voltage range of
3.0V to 13.2V, independent of the IC supply. The output
voltage is adjustable down to 0.8V. The IC operates at
a fixed 300kHz switching frequency and provides up to
25A of output current with efficiency up to 95%. This
controller has excellent transient response resulting in
smaller output capacitance.
The MAX1954A features foldback current limiting that
greatly reduces input current and component power
dissipation during output overload or short-circuit
conditions.
The compensation and shutdown control (COMP) input,
in addition to providing compensation to the error
amplifier, can be pulled low to shut down the converter.
An input undervoltage lockout is provided to ensure
proper operation during power sags to prevent the
external power MOSFETs from overheating. Internal
digital soft-start is included to reduce inrush current
and save an external capacitor.
The MAX1954A is available in a tiny 10-pin µMAX®
package to minimize PC board space.
Applications
Printers and Scanners
Graphic Cards and Video Cards
PCs and Servers
Microprocessor Cores
Low-Voltage Distributed Power
Telecom/Networks
FeaturesCurrent-Mode ControllerFixed-Frequency PWMFoldback Current LimitOutput Down to 0.8V with ±1% FB Accuracy3.0V to 13.2V Input Voltage300kHz Switching Frequency25A Output-Current Capability93% EfficiencyAll-N-Channel-MOSFET Design for Low CostNo Current-Sense Resistor NeededInternal Digital Soft-StartSmall 10-Pin µMAX Package
MAX1954A
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limit
TOP VIEW
BST
PGNDGND
COMP
HSD
MAX1954A
μMAXIN
Pin Configuration
19-3154; Rev 1; 5/05
Ordering InformationPART TEMP RANGE PIN-PACKAGE
MAX1954AEUB-40°C to +85°C10 µMAX
MAX1954AEUB+-40°C to +85°C10 µMAX
EVALUATION KITAVAILABLE
µMAX is a registered trademark of Maxim Integrated Products, Inc.
+Denotes lead-free package.
MAX1954A
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limit
ABSOLUTE MAXIMUM RATINGS
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.
IN, FB to GND...........................................................-0.3V to +6V
LX to BST..................................................................-6V to +0.3V
BST to GND............................................................-0.3V to +20V
DH to LX...................................................-0.3V to (VBST+ 0.3V)
DL, COMP to GND.......................................-0.3V to (VIN+ 0.3V)
HSD to GND..............................................................-0.3V to 14V
PGND to GND.......................................................-0.3V to +0.3V
Continuous Power Dissipation (TA= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C)...........444mW
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
(VIN = 5V, VBST - VLX = 5V, TA= 0°C to +85°C,unless otherwise noted.)PARAMETER CONDITIONS MIN TYP MAX UNITSGENERAL Operating Input Voltage Range 3.0 5.5 VHSD Voltage Range (Note 1) 3.0 13.2 VQuiescent Supply Current VFB = 1.5V 1 2 mAStandby Supply Current VIN = VBST = 5.5V, VHSD = 13.2V, LX = unconnected,
COMP = GND 2 mAUndervoltage-Lockout Trip Level Falling VIN, 50mV (typ) hysteresis 2.5 2.7 2.9 VDC-DC CONTROLLER Output-Voltage Adjust Range
(VOUT) Maximum output voltage depends on external components
and maximum duty cycle 0.8 VERROR AMPLIFIER FB Regulation Voltage -1.0 +0.8 +1.0 %Transconductance 70 110 160 µSVoltage Gain 200 V/ V FB Input Leakage Current VFB = 0.9V 50 500 NAFB Input Common-Mode Range -0.1 +1.5 VCOMP Output-Voltage Swing 0.80 2.36 VCurrent-Sense Amplifier
Voltage Gain 3.15 3.5 3.85 V / V VFB = 0.8V 110 135 145 Current-Limit Threshold VPGND - VLX VFB = 0V 21 36 51 mVOSCILLATOR Switching Frequency MAX1954A 240 300 360 kHzMaximum Duty Cycle Measured at DH 89 91 93 %Minimum Duty Cycle VCOMP = 1.25V, LX = GND, VBST = VIN = 3.3V 2.5 3 %
MAX1954A
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limit
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 5V, VBST - VLX = 5V, TA= 0°C to +85°C,unless otherwise noted.)PARAMETER CONDITIONS MIN TYP MAX UNITSSOFT-START Soft-Start Period 3.4 msSoft-Start Levels 12.5 mVFET DRIVERS DH, DL Output Low Voltage ISINK = 10mA 0.1 VDH, DL Output High Voltage ISOURCE = 10mA V IN - 0.1V or BS T - 0.1V VDH Pullup/Pulldown, DL Pullup On-Resistance 1.5 3 ΩDL Pulldown On-Resistance 1 2 ΩLX, BST, HSD Leakage Current VBST = 18.7V, VLX = 13.2V, VIN = 5.5V, VHSD = 13.2V 30 µATHERMAL PROTECTION Thermal Shutdown Rising temperature, 15°C hysteresis +160 °CSHUTDOWN CONTROL COMP Logic-Level Low 3V < VIN < 5.5V 0.25 VCOMP Logic-Level High 3V < VIN < 5.5V 0.8 VCOMP Pullup Current 100 µA
ELECTRICAL CHARACTERISTICS
(VIN = 5V, VBST - VLX = 5V, TA= -40°C to +85°C,unless otherwise noted.) (Note 2)PARAMETER CONDITIONS MIN MAX UNITSGENERAL Operating Input Voltage Range 3.0 5.5 VHSD Voltage Range (Note 1) 3.0 13.2 VQuiescent Supply Current VFB = 1.5V 2 mAStandby Supply Current VIN = VBST = 5.5V, VHSD = 13.2V, LX = unconnected,
COMP = GND 2 mAUndervoltage Lockout Trip Level Rising VIN 3% (typ) hysteresis 2.50 2.93 VDC-DC CONTROLLER Output-Voltage Adjust Range
(VOUT) 0.8 0.9 x VIN VERROR AMPLIFIER FB Regulation Voltage -2.5 +1.0 %Transconductance 70 160 µSFB Input Leakage Current VFB = 0.9V 500 NAFB Input Common-Mode Range -0.1 +1.5 VCOMP Output-Voltage Swing 0.8 2.2 V
MAX1954A
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limit
Note 1:HSD and IN are externally connected for applications where HSD < 5.5V.
Note 2:Specifications to -40°C are guaranteed by design and not production tested.
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 5V, VBST - VLX = 5V, TA= -40°C to +85°C,unless otherwise noted.) (Note 2)PARAMETER CONDITIONS MIN MAX UNITSCurrent-Sense Amplifier
Voltage Gain 3.15 3.85 V/VVFB = 0.8V 110 145 Current-Limit Threshold VPGND - VLX, MAX1954A VFB = 0V 21 51 mVOSCILLATOR Switching Frequency 240 360 kHzMaximum Duty Cycle Measured at DH 89 93 %Minimum Duty Cycle VCOMP = 1.25V, LX = GND, VBST = VIN = 3.3V 3 %FET DRIVERS DH, DL Output Low Voltage ISINK = 10mA 0.1 VDH, DL Output High Voltage ISOURCE = 10mA V IN - 0.1V or BS T - 0.1V VDH Pullup/Pulldown,DL Pullup On-Resistance 3 ΩDL Pulldown On-Resistance 2 ΩLX, BST, HSD Leakage Current VBST = 18.7V, VLX = 13.2V, VIN = 5.5V, VHSD = 13.2V 30 µASHUTDOWN CONTROL COMP Logic-Level Low 3V < VIN < 5.5V 0.25 VCOMP Logic-Level High 3V < VIN < 5.5V 0.8 VCOMP Pullup Current 100 µA
MAX1954A
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limit
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
EFFICIENCY
vs. LOAD CURRENT
MAX1954A toc01
LOAD CURRENT (A)
EFFICIENCY (%)
VOUT = 2.5V
VIN = VHSD = 5V
VOUT = 1.5V
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1954A toc02
LOAD CURRENT (A)
OUTPUT VOLTAGE (V)
VIN = VHSD = 5V
OUTPUT VOLTAGE CHANGE
vs. INPUT VOLTAGE
MAX1954A toc03
INPUT VOLTAGE (V)
CHANGE IN OUTPUT VOLTAGE (mV)
VOUT = 2.5V
VOUT = 0.8V
VIN = VHSD
IOUT = 5A
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
MAX1954A toc04
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
VIN = VHSD
IOUT = 5A
OSCILLATOR FREQUENCY
vs. INPUT VOLTAGE
MAX1954A toc05
INPUT VOLTAGE (V)
OSCILLATOR FREQUENCY (kHz)
TA = -40°C
TA = +85°CTA = +25°C
VIN = VHSD
LOAD TRANSIENT
MAX1954A toc06
40μs/div
100mV/divVOUT
AC-COUPLED
IOUT
5A/μs
500mA
MAX1954A
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limitypical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
LOAD TRANSIENT
MAX1954A toc07
40μs/div
100mV/divVOUT
AC-COUPLED
IOUT
5A/μs
2.5A
NO-LOAD SWITCHING WAVEFORMS
MAX1954A toc08
2μs/div
2A/divIL
5V/div
10V/div
5V/div
HEAVY-LOAD SWITCHING WAVEFORMS
ILOAD = 5A
MAX1954A toc09
2μs/div
2A/divIL
5V/div
10V/div
5V/div
SHORT CIRCUIT AND RECOVERY
MAX1954A toc11
200μs/div
1V/divVOUT
VIN
ILX5A/div
2V/div
IIN2A/div
POWER-UP/POWER-DOWN WAVEFORMS
MAX1954A toc10
4ms/div
5V/divVIN
VOUT
ILX5A/div
2V/div
STARTUP INTO PREBIASED OUTPUT
(OUTPUT PREBIASED AT ~1.7V)
MAX1954A toc12
2ms/div
1V/divVOUT
VIN5V/div
5V/div5V/div
MAX1954A
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limit
Detailed Description
The MAX1954A single-output, current-mode, PWM, step-
down DC-DC controller features foldback current limit
and switches at 300kHz for high efficiency. The
MAX1954A is designed to drive a pair of external N-
channel power MOSFETs in a synchronous buck topolo-
gy to improve efficiency and cost compared with a
P-channel power-MOSFET topology. The on-resistance
of the low-side MOSFET is used for short-circuit current-
limit sensing, while the high-side MOSFET’s on-resis-
tance is used for current-mode feedback, thus
eliminating the need for current-sense resistors. The
short-circuit current limit is fixed at 135mV. The foldback
current scheme reduces the input current during short-
circuit and severe-overload conditions. The MAX1954A
is configured with a high-side drain input (HSD) allowing
an extended input voltage range of 3V to 13.2V that is
independent of the IC input supply (Figure 1).
DC-DC Converter Control Architecture
The MAX1954A step-down converter uses a PWM, cur-
rent-mode control scheme. An internal transconductance
amplifier establishes an integrated error voltage. An
open-loop comparator compares the integrated voltage-
feedback signal against the amplified current-sense sig-
nal plus the slope compensation ramp, which is summed
into the main PWM comparator to preserve inner-loop sta-
bility and eliminate inductor staircasing. At each rising
edge of the internal clock, the high-side MOSFET turns on
until the PWM comparator trips or the maximum duty
cycle is reached. During this on-time, current ramps up
through the inductor, storing energy in a magnetic field
and sourcing current to the output. The current-mode
feedback system regulates the peak inductor current as a
function of the output-voltage error signal. The circuit acts
as a switch-mode transconductance amplifier because
the average inductor current is close to the peak inductor
current (assuming the inductor is large enough to provide
a reasonably small ripple current). This pushes the output
inductance-capacitance filter pole normally found in a
voltage-mode PWM to a higher frequency.PIN NAME FUNCTION1 HSD High-Side Drain Current-Sense Input. HSD senses the voltage at the drain of the high-side, N-channel MOSFET.
Connect to the high-side MOSFET drain using a Kelvin connection.2 COMPCompensation and Shutdown Control Pin. Connect appropriate RC networks to compensate the control loop.
Pull to GND to shut down the IC. See the Compensation Design section for instructions on calculating the RC
values.3 FBFeedback Input. Regulates at VFB = 0.8V. Connect FB to the center tap of a resistor-divider from the output to
GND to set the output voltage.4 GND Ground5 INIC Supply Voltage. Provides power for the IC. Connect to a 3V to 5.5V power supply. Bypass to GND with a
0.22µF ceramic capacitor and to PGND with a 1µF ceramic capacitor.6 DLLow-Side Gate-Drive Output. Drives the synchronous-rectifier MOSFET. Swings from 0 to VIN. DL is low in
shutdown and UVLO.7 PGND Power Ground8 DH High-Side Gate-Drive Output. Drives the high-side N-channel MOSFET. DH is a floating driver output that swings
from VLX to VBST. DH is low in shutdown and UVLO.9 LX Controller Current-Sense Input. Connect LX to the junction of the MOSFETs and inductor. LX is the reference
point for the current limit.10 BSTHigh-Side MOSFET Supply Input. Connect a 0.1µF ceramic capacitor from BST to LX to supply the necessary
gate drive for the high-side N-channel MOSFET.
Pin Description
MAX1954A
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limit
During the second half of the cycle, the high-side
MOSFET turns off and the low-side MOSFET turns on. The
inductor releases the stored energy as the current ramps
down, providing current to the output. The output capaci-
tor stores charge when the inductor current exceeds the
required load current and discharges when the inductor
current is lower, smoothing the voltage across the load.
Under overload conditions, when the inductor current
exceeds the current limit (see the Current-LimitCircuit
section), the high-side MOSFET is not turned on at the ris-
ing clock edge and the low-side MOSFET remains on to
let the inductor current ramp down.
The MAX1954A operates in a forced-PWM mode; there-
fore, the controller maintains a constant switching fre-
quency, regardless of load, to allow for easier post-
filtering of the switching noise.
Current-Sense Amplifier
The current-sense circuit amplifies the current-sense
voltage (the high-side MOSFET’s on-resistance
(RDS(ON)) multiplied by the inductor current). This ampli-
fied current-sense signal and the internal slope-compen-
sation signal are summed (VSUM) together and fed into
the PWM comparator’s inverting input. The PWM com-
parator shuts off the high-side MOSFET when VSUM
exceeds the integrated feedback voltage (VCOMP).
REFERENCE
AND
SOFT-START
DIGITAL-TO-ANALOG
CONVERTER
FOLDBACK CURRENT-
LIMIT CIRCUITRY
COMP
0.5V
SHUTDOWN
COMPARATOR
ERROR
AMPLIFIER
SLOPE
COMPENSATION
THERMAL
LIMITUVLO
PWM
CONTROL
CIRCUITRY
CLOCK
SHORT-CIRCUIT
CURRENT-LIMIT
CIRCUITRY
CURRENT-LIMIT
COMPARATOR
PGND
2.36V
CLAMP
GND
CURRENT-
SENSE
CIRCUITRY
BST
HSD
MAX1954A
Functional Diagram
MAX1954A
Low-Cost, Current-Mode PWM Buck
Controller with Foldback Current Limit
Place the high-side MOSFET as close as possible to
the controller and connect HSD and LX to the MOSFET
using Kelvin-sense connections to guarantee current-
sense accuracy and improve stability.
Current-Limit Circuit
The current-limit circuit employs a lossless, foldback,
valley current-limiting algorithm that uses the low-side
MOSFET’s on-resistance as the sensing element. Once
the high-side MOSFET turns off, the voltage across the
low-side MOSFET is monitored. If the voltage across the
low-side MOSFET (RDS(ON)x IINDUCTOR) does not
exceed the current limit, the high-side MOSFET turns on
normally. In this condition, the output drops smoothly out
of regulation. If the voltage across the low-side MOSFET
exceeds the current-limit threshold at the beginning of a
new oscillator cycle, the low-side MOSFET remains on
and the high-side MOSFET remains off.
Typical Application Circuits
HSD
COMPC4C2R1
GND
BST
PGND
MAX1954AVOUT
1.8V
VIN
3V TO 5.5V
VHSD
5.5V TO 13.2V
Figure 1. MAX1954A Typical Application Circuit
COMP
0.8μH
0.1μF
15pF
270kΩ
560pF
0.22μF
C15
C14R1
10kΩ
C8–C13
270μF
C2–C6
10μF
8.06kΩ
GND
BST
PGND
HSD
MAX1954AVOUT
+1.8V AT 20A
VHSD
10.8V TO 13.2VVIN
3V TO 5.5VN4
Figure 2. MAX1954A Circuit Capable of 20A Output

Partno	Mfg	Dc	Qty	Available	Descript
MAX1954AEUB+ \|MAX1954AEUB	MAXIM	N/a	22960	avai	Low-Cost, Current-Mode PWM Buck Controller with Foldback Current Limit