MAX1626 ,5V/3.3V or Adjustable, 100% Duty Cycle, High-Efficiency, Step-Down DC-DC ControllersApplications• External P-Channel MOSFET Allows Output Power• Handheld Computersof > 12.5W• High-Eff ..
MAX1626ESA ,5V/3.3V or Adjustable / 100% Duty-Cycle / High-Efficiency / Step-Down DC-DC ControllersMAX1626/MAX162719-1075; Rev 0; 6/965V/3.3V or Adjustable, 100% Duty-Cycle, High-Efficiency, Step-Do ..
MAX1626ESA+ ,5V/3.3V or Adjustable, 100% Duty Cycle, High-Efficiency, Step-Down DC-DC ControllersEVALUATION KIT AVAILABLE5V/3.3V or Adjustable,MAX1626/MAX1627100% Duty-Cycle, High-Efficiency,Step- ..
MAX1626ESA+T ,5V/3.3V or Adjustable, 100% Duty Cycle, High-Efficiency, Step-Down DC-DC ControllersApplications • Soft-Start Limits Startup Current• Current-Limited Control Scheme• 5V to 3.3V Green ..
MAX1626ESA-T ,5V/3.3V or Adjustable, 100% Duty Cycle, High-Efficiency, Step-Down DC-DC ControllersApplications• Increase Design Flexibility• Battery-Powered
MAX1626ESA-T ,5V/3.3V or Adjustable, 100% Duty Cycle, High-Efficiency, Step-Down DC-DC ControllersElectrical CharacteristicsPARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSInput Voltage Range V+ 3.0 1 ..
MAX436CPD ,Wideband Trasconductance AmplifiersFeatures
. 275MHz Bandwidth (MAX435)
. tb50Wps Slew Rate
ta
. No Feedback
. True Differentia ..
MAX436CSD ,Wideband Trasconductance AmplifiersApplications
High-Speed Instrumentation Amplifiers
High-Speed Filters
Wideband, High-Gain Bandpa ..
MAX436EPD ,Wideband Trasconductance Amplifiersapplications, sucn a5 lllgll'apku "F%Pbtbr0r's'''""'"''"' -
plitiers and wideband, high-gain bandp ..
MAX436ESD ,Wideband Trasconductance AmplifiersELECTRICAL CHARACTERISTICS - MAX435
(V+ = W, V- = -5v, -2.5vs IN+ s 2.5V, -2.5V s IN- s 2.5V, ZL+ ..
MAX436ESD+T ,250MHz Wideband Transconductance Amplifier with Differential Output Not Recommended for New Designs This product was manufactured for Maxim by an outside wafer foun ..
MAX436ESD-T ,250MHz Wideband Transconductance Amplifier with Differential Output Not Recommended for New Designs This product was manufactured for Maxim by an outside wafer foun ..
MAX1626-MAX1627
5V/3.3V or Adjustable, 100% Duty Cycle, High-Efficiency, Step-Down DC-DC Controllers
MAX1626/MAX16275V/3.3V or Adjustable,
100% Duty-Cycle, High-Efficiency,
Step-Down DC-DC ControllersEVALUATION KIT AVAILABLE
General DescriptionThe MAX1626/MAX1627 step-down DC-DC controllers
operate over a 2.6V to 16.5V input voltage range. The
controllers deliver load current from 1mA to more than
2A. The MAX1626 has pin-selectable 3.3V and 5V out-
puts. The MAX1627 supports adjustable outputs from
1.3V to 16V.
A unique current-limited, pulse-frequency-modulation
(PFM) control scheme operates up to 100% duty cycle,
resulting in very low dropout voltage. This control
scheme eliminates minimum load requirements and
reduces supply current under light loads to 90µA
(versus 2mA to 10mA for common pulse-width modula-
tion controllers).
The devices are available in a 8-pin SOIC package
(-40°C to +85°C) and dice (0°C to +70°C).
Applications5V to 3.3V Green PC ApplicationsBattery-Powered ApplicationsHandheld ComputersHigh-Efficiency Step-Down RegulationLow-Cost Notebook Computer SuppliesMinimum Component DC-DC ConvertersPCMCIA Power SuppliesPDAs and Other Handheld DevicesPortable Terminals
Benefits and FeaturesReduce External Components and Total Cost300KHz PWM Switching Reduces Component SizeTiny Surface-Mount Inductor
Reduce Power Dissipation> 90% Efficiency from 3mA to 2A LoadsLow Dropout Voltage100% Maximum Duty Cycle
Reduce Number of DC-DC Controllers to StockWide 2.6V to 16.5V Input Voltage OptionsSelectable 3.3V and 5V or Adjustable 1.3V to 16V
Output Voltage Options
Reduce System Power Consumption90µA Max Quiescent Current1µA Max Shutdown Current
Operates Reliably in Adverse EnvironmentSoft-Start Limits Startup CurrentCurrent-Limited Control Scheme
Increase Design FlexibilityExternal P-Channel MOSFET Allows Output Power
of > 12.5W
MAX1626SHDN
GND
3/5
ON/OFFEXT
REFOUT
OUTPUT
3.3V
INPUT
3.3V to 16.5V
Pin ConfigurationGND
EXTREF
SHDN
3/5 (FB)
OUT
( ) ARE FOR MAX1627
TOP VIEW
MAX1626
MAX1627
Typical Operating Circuit
PART
MAX1626C/DMAX1626ESA
MAX1627C/D0°C to +70°C
-40°C to +85°C
0°C to +70°C
TEMP RANGEPIN-PACKAGEDice*
8 SO
Dice*
Ordering Information* Dice are tested at TA= +25°C.
MAX1627ESA-40°C to +85°C8 SO
MAX1626/MAX16275V/3.3V or Adjustable,
100% Duty-Cycle, High-Efficiency,
Step-Down DC-DC Controllers
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.
Supply Voltage, V+ to GND.......................................-0.3V, +17V
OUT, FB, 3/5, SHDN, REF, CS, EXT to GND...-0.3V, (V+ + 0.3V)
Maximum Current at REF (IREF)..........................................15mA
Maximum Current at EXT (IEXT)..........................................50mA
Continuous Power Dissipation (TA= +70°C)
SO (derate 5.88mW/°C above +70°C)..........................471mW
Operating Temperature Range
MAX1626ESA/MAX1627ESA............................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
0µA ≤IREF≤100µA
ILOAD= 0µA
30mA < ILOAD< 2.0A, V+ = 8V
V+ = SHDN = 16.5V (shutdown)
6.0V < V+ < 12.0V, ILOAD= 1A
Operating, no load
Output in regulation
Output forced to 0V
V+ = 5V
3/5 = 0V or V+
MAX1627
Circuit of Figure 1, 3/5 = V+ (Note 1)
MAX1626, 3/5 = V+, output forced to 5V
SHDN = 0V or V+
MAX1627, includes hysteresis
CONDITIONS410REF Load Regulation1.271.301.33VREFReference Voltage
mV/A15Load Regulation
mV/V5Line Regulation100EXT Duty-Cycle Limit1.52.02.5
81012Minimum EXT Off Time10EXT Resistance±13/5 Leakage Current0.53/5 Input Voltage LowV+ - 0.53/5 Input Voltage High±1SHDN Input Current0.4SHDN Input Voltage Low1I+Supply Current into V+70903.016.5V+Input Voltage Range1.6SHDN Input Voltage High85100115VCSCS Threshold Voltage010CS Input Current035FB Leakage Current2.72.8Undervoltage Lockout
4.855.005.15243750IOUTOUT Input Current1.271.301.33FB Threshold Voltage
UNITSMINTYPMAXSYMBOLPARAMETERV+ = 3V to 16.5V, ILOAD= 0µAµV/V10100REF Line Regulation
Circuit of Figure 1, 3/5 = 0V (Note 1)V3.203.303.40VOUTOutput Voltage
MAX1626/MAX16275V/3.3V or Adjustable,
100% Duty-Cycle, High-Efficiency,
Step-Down DC-DC Controllers
Electrical Characteristics
Note 1:V+ must exceed VOUTto maintain regulation.
Note 2:Specifications from 0°C to -40°C are guaranteed by design, not production tested.
V+ = SHDN = 16.5V (shutdown)
Operating, no load
ILOAD= 0µA
MAX1627
Circuit of Figure 1, 3/5 = V+
MAX1626, 3/5 = V+, output forced to 5V
MAX1627, includes hysteresis
CONDITIONS2IOUTSupply Current into V+1003.016.5V+Input Voltage 1.251.35Reference80120CS Threshold Voltage050FB Leakage Current2.9Undervoltage Lockout
4.805.202450IOUTOUT Input Current1.251.35FB Threshold Voltage
UNITSMINTYPMAXSYMBOLPARAMETERCircuit of Figure 1, 3/5 = 0VV3.163.44VOUTOutput Voltage
0.1m100m11m10m10
EFFICIENCY vs. LOAD CURRENT
(VOUT = +3.3V)MAX1626-05
LOAD CURRENT (A)
EFFICIENCY (%)40
A: V+ = +4.3V
B: V+ = +5V
C: V+ = +8V
D: V+ = +10V
E: V+ = +12V
F: V+ = +15VCIRCUIT OF FIGURE 1CEF
0.1m100m11m10m10
EFFICIENCY vs. LOAD CURRENT
(VOUT = +5V)MAX1626-03
LOAD CURRENT (A)
EFFICIENCY (%)40
A: V+ = +6V
B: V+ = +8V
C: V+ = +10V
D: V+ = +12V
E: V+ = +15VCIRCUIT OF FIGURE 1BCE
DROPOUT VOLTAGE
vs. LOAD CURRENT
MAX1626-11
LOAD (A)
DROPOUT VOLTAGE (V)
3.3V SETTING
VOUT = +3.17V
5V SETTING
VOUT = +4.8V
Typical Operating Characteristics
MAX1626/MAX16275V/3.3V or Adjustable,
100% Duty-Cycle, High-Efficiency,
Step-Down DC-DC Controllers
MAX1626 SHUTDOWN CURRENT
vs. TEMPERATURE
MAX1626-04
TEMPERATURE (°C)
SHUTDOWN CURRENT (
APPLICATION CIRCUIT
SHUTDOWN CURRENT:
A: V+ = +15V
B: V+ = +10V
C: V+ = +4V
MAX1626 SHUTDOWN
CURRENT:
D: V+ = +16V
E: V+ = +4V
EXT RISE AND FALL TIMES
vs. CAPACITANCE
MAX1626-10
CAPACITANCE (pF)
tRISE
AND t
FALL
(ns)
tRISE, V+ = +15V
tFALL, V+ = +5V
tRISE, V+ = +5V
tFALL, V+ = +15V
EXT RISE AND FALL TIMES
vs. TEMPERATURE
MAX1626-09
TEMPERATURE (°C)
RISE
AND t
FALL
(ns)2080
tFALL, V+ = +5V
CEXT = 1nF
3/5 = 0V
OUT = 50kHz, 0.3Vp-p, 3.3VDC
tRISE, V+ = +5V
tRISE, tFALL, V+ = +15V
MAX1626
V+ QUIESCENT CURRENT
vs. TEMPERATURE
MAX1626-01
3/5 = 0V
OUT FORCED TO 3.4V
V+ = +16V
V+ = +10V
V+ = +4V12345
MAX1626 EXT OFF TIME
vs. OUTPUT VOLTAGEMAX1626-02
OUTPUT VOLTAGE (V)
EXT OFF TIME (
V+ = +5V
3/5 = GND
3/5 = V+0.20.40.60.81.01.21.4
MAX1627 EXT OFF TIME
vs. FB PIN VOLTAGEMAX1626-03
FB PIN VOLTAGE (V)
EXT OFF TIME (
V+ = +5V
CS TRIP LEVEL vs. TEMPERATURE
MAX1626-12
CS TRIP LEVEL (mV)
OUT = 0V
Typical Operating Characteristics (continued)
MAX1626/MAX16275V/3.3V or Adjustable,
100% Duty-Cycle, High-Efficiency,
Step-Down DC-DC Controllers
REFERENCE OUTPUT VOLTAGE
vs. TEMPERATURE
MAX1626-13
TEMPERATURE (°C)
REFERENCE OUTPUT VOLTAGE (V)
IREF = 10µA
IREF = 0µA
IREF = 50µA
IREF = 100µA
100µs/div
MAX1626 LOAD-TRANSIENT RESPONSEMAX1626-15
V+ = 8V, VOUT = 3.3V, LOAD = 30mA to 2A
A: OUT, 50mV/div, 3.3V DC OFFSET
B: LOAD CURRENT, 1A/div
5ms/div
MAX1626 LINE-TRANSIENT RESPONSEMAX1626-16
VOUT = 5V, LOAD = 1A, CIN = 33µF
A: OUT, 100mV/div, 5V DC OFFSET
B: V+ 6V to 12V, 2V/div
5ms/div
LINE-TRANSIENT RESPONSE
FROM 100% DUTY CYCLEMAX1626-17
VOUT = 3.3V, LOAD = 1A, CIN = 47µF
A: OUT, 100mV/div, 3.3V DC OFFSET
B: V+ 3.3V to 15V, 5V/div
500µs/div
MAX1626 SHUTDOWN RESPONSE TIME
AND SUPPLY CURRENTMAX1626-14
V+ = 8V, VOUT = 5V, LOAD = 1A
A: OUT, 2V/div
B: SUPPLY CURRENT, 1A/div
C: SHDN, 5V/div
Typical Operating Characteristics (continued)
MAX1626/MAX16275V/3.3V or Adjustable,
100% Duty-Cycle, High-Efficiency,
Step-Down DC-DC Controllers
Pin DescriptionGround88
1.3V Reference Output. Can source 100µA. Bypass with 0.1µF.44
Positive Supply Input. Bypass with 0.47µF.55
Current-Sense Input. Connect current-sense resistor between V+ and CS. External
MOSFET is turned off when the voltage across the resistor equals the current-limit
trip level (around 100mV).6
Gate Drive for External P-Channel MOSFET. EXT swings between V+ and GND.77
Active-High Shutdown Input. Device is placed in shutdown when SHDN is driven
high. In shutdown mode, the reference, output, and external MOSFET are turned off.
Connect to GND for normal operation.3
3.3V or 5V Selection. Output voltage is set to 3.3V when this pin is low or 5V when it
is high.—2
Feedback Input for adjustable-output operation. Connect to an external voltage
divider between the output and GND (see the Setting the Output Voltage section).2—
Sense input for fixed 5V or 3.3V output operation. OUT is internally connected to an
on-chip voltage divider (MAX1626). It does not supply current. Leave OUT uncon-
nected during adjustable-output operation (MAX1627).1
GND
REF
EXT
SHDN
3/5
OUT
MAX1626
0.47µF
RSENSE
0.04Ω
U1
LOGIC-LEVEL MOSFET
0.1µF
3/5
SHDN
REF
EXT
GNDOUT
INPUT
L1
22µH, 3A
220µF
LOW-ESR
TANTALUM
68µF LOW-ESR
TANTALUM
68µF LOW-ESR
TANTALUM
L1: SUMIDA CDRH125-220
D1: NIHON NSQ03A03
U1: MORTOLA MMSF3PO2HD
OUTPUT
Figure 1. MAX1626 Typical Operating Circuit
MAX1626
MAX1627MINIMUM ON-TIME
ONE-SHOT
OUT
(FB)
3/5
SHDN
TRIGQ
MINIMUM OFF-TIME
ONE-SHOT
CURRENT-SENSE
COMPARATOR
ERROR
COMPARATORREF
1.5V
EXTREF
( ) MAX1627 ONLY
MAX1626 ONLY
TRIGQ
Figure 2. Simplified Functional Diagram
PIN
MAX1626
FUNCTION
MAX1627
NAME
MAX1626/MAX16275V/3.3V or Adjustable,
100% Duty-Cycle, High-Efficiency,
Step-Down DC-DC Controllers
Detailed DescriptionThe MAX1626/MAX1627 are step-down DC-DC con-
trollers designed primarily for use in portable comput-
ers and battery-powered devices. Using an external
MOSFET and current-sense resistor allows design flexi-
bility and the improved efficiencies associated with
high-performance P-channel MOSFETs. A unique, cur-
rent-limited, pulse-frequency-modulated (PFM) control
scheme gives these devices excellent efficiency over
load ranges up to three decades, while drawing around
90µA under no load. This wide dynamic range opti-
mizes the MAX1626/MAX1627 for battery-powered
applications, where load currents can vary consider-
ably as individual circuit blocks are turned on and off to
conserve energy. Operation to a 100% duty cycle
allows the lowest possible dropout voltage, extending
battery life. High switching frequencies and a simple
circuit topology minimize PC board area and compo-
nent costs. Figure 1 shows a typical operating circuit
for the MAX1626.
PFM Control SchemeThe MAX1626/MAX1627 use a proprietary, third-genera-
tion, current-limited PFM control scheme. Improvements
include a reduced current-sense threshold and operation
to a 100% duty cycle. These devices pulse only as need-
ed to maintain regulation, resulting in a variable switching
frequency that increases with the load. This eliminates the
current drain associated with constant-frequency pulse-
width-modulation (PWM) controllers, caused by switching
the MOSFET unnecessarily.
When the output voltage is too low, the error compara-
tor sets a flip-flop, which turns on the external P-chan-
nel MOSFET and begins a switching cycle (Figures 1
and 2). As shown in Figure 3, current through the
inductor ramps up linearly, storing energy in a magnet-
ic field while dumping charge into an output capacitor
and servicing the load. When the MOSFET is turned off,
the magnetic field collapses, diode D1 turns on, and
the current through the inductor ramps back down,
transferring the stored energy to the output capacitor
and load. The output capacitor stores energy when the
inductor current is high and releases it when the induc-
tor current is low.
The MAX1626/MAX1627 use a unique feedback and
control system to govern each pulse. When the output
voltage is too low, the error comparator sets a flip-flop,
which turns on the external P-channel MOSFET. The
MOSFET turns off when the current-sense threshold is
exceeded or when the output voltage is in regulation. A
one-shot enforces a 2µs minimum on-time, except in
current limit. The flip-flop resets when the MOSFET
turns off. Otherwise the MOSFET remains on, allowing a
duty cycle of up to 100%. This feature ensures the low-
est possible dropout. Once the MOSFET is turned off,
the minimum off-time comparator keeps it off. The mini-
mum off-time is normally 2µs, except when the output is
significantly out of regulation. If the output is low by
30% or more, the minimum off-time increases, allowing
soft-start. The error comparator has 0.5% hysteresis for
improved noise immunity.
In the MAX1626, the 3/5 pin selects the output voltage
(Figure 2). In the MAX1627, external feedback resistors
at FB adjust the output.
Operating ModesWhen delivering low and medium output currents, the
MAX1626/MAX1627 operate in discontinuous-conduc-
tion mode. Current through the inductor starts at zero,
rises as high as the peak current limit set by the cur-
rent- sense resistor, then ramps down to zero during
each cycle (Figure 3). Although efficiency is still excel-
lent, output ripple increases and the switch waveform
exhibits ringing. This ringing occurs at the resonant fre-
quency of the inductor and stray capacitance, due to
residual energy trapped in the core when the commuta-
tion diode (D1 in Figure 1) turns off. It is normal and
poses no operational problems.
When delivering high output currents, the MAX1626/
MAX1627 operate in continuous-conduction mode
(Figure 4). In this mode, current always flows through
the inductor and never ramps to zero. The control cir-
cuit adjusts the switch duty cycle to maintain regulation
without exceeding the peak switching current set by
the current-sense resistor. This provides reduced out-
put ripple and high efficiency.
100% Duty Cycle and DropoutThe MAX1626/MAX1627 operate with a duty cycle up
to 100%. This feature extends usable battery life by
turning the MOSFET on continuously when the supply
voltage approaches the output voltage. This services
the load when conventional switching regulators with
less than 100% duty cycle would fail. Dropout voltage
is defined as the difference between the input and out-
put voltages when the input is low enough for the out-
put to drop out of regulation. Dropout depends on the
MOSFET drain-to-source on-resistance, current-sense
resistor, and inductor series resistance, and is propor-
tional to the load current:
Dropout Voltage=
I x R + R+ ROUTDS(ON)SENSEINDUCTOR[]
MAX1626/MAX16275V/3.3V or Adjustable,
100% Duty-Cycle, High-Efficiency,
Step-Down DC-DC Controllers
EXT Drive Voltage RangeEXT swings from V+ to GND and provides the gate
drive for an external P-channel power MOSFET. A high-
er supply voltage increases the gate drive to the
MOSFET and reduces on-resistance (RDS(ON)). See
External Switching Transistorsection.
Quiescent CurrentThe device’s typical quiescent current is 70µA.
However, actual applications draw additional current to
supply MOSFET switching currents, OUT pin current, or
external feedback resistors (if used), and both the diode
and capacitor leakage currents. For example, in the cir-
cuit of Figure 1, with V+ at 7V and VOUTat 5V, typical
no-load supply current for the entire circuit is 84µA.
When designing a circuit for high-temperature opera-
tion, select a Schottky diode with low reverse leakage.
Shutdown ModeWhen SHDN is high, the device enters shutdown mode.
In this mode, the feedback and control circuit, reference,
and internal biasing circuitry are turned off. EXT goes
high, turning off the external MOSFET. The shutdown
supply current drops to less than 1µA. SHDN is a logic-
level input. Connect SHDN to GND for normal operation.
ReferenceThe 1.3V reference is suitable for driving external loads,
such as an analog-to-digital converter. It has a guaran-
teed 10mV maximum load regulation while sourcing load
currents up to 100µA. The reference is turned off during
shutdown. Bypass the reference with 0.1µF for normal
operation. Place the bypass capacitor within 0.2 inches
(5mm) of REF, with a direct trace to GND (Figure 7).
Soft-StartSoft-start reduces stress and transient voltage slumps
on the power source. When the output voltage is near
ground, the minimum off-time is lengthened to limit peak
switching current. This compensates for reduced nega-
tive inductor current slope due to low output voltages.
Design Information
Setting the Output VoltageThe MAX1626’s output voltage can be selected to 3.3V
or 5V under logic control by using the 3/5 pin. The 3/5
pin requires less than 0.5V to ensure a 3.3V output, or
more than (V+ - 0.5)V to guarantee a 5V output. The
voltage sense pin (OUT) must be connected to the out-
put for the MAX1626.
The MAX1627’s output voltage is set using two resis-
tors, R2 and R3 (Figure 5), which form a voltage divider
between the output and GND. R2 is given by:
where VREF= 1.3V. Since the input bias current at FB
has a maximum value of 50nA, large values (10kΩto
200kΩ) can be used for R3 with no significant accuracy= R3 x V
OUT
REF⎛⎜⎟1
10µs/div
CIRCUIT OF FIGURE 1, V+ = 8V, VOUT = 5V, LOAD = 100mA
A: MOSFET DRAIN, 5V/div
B: OUT, 50mV/div, 5V DC OFFSET
C: INDUCTOR CURRENT, 1A/div
Figure 3. Discontinuous-Conduction Mode, Light-Load-Current
Waveform
10µs/div
CIRCUIT OF FIGURE 1, V+ = 8V, VOUT = 5V, LOAD = 1.5A
A: MOSFET DRAIN, 5V/div
B: OUT, 50mV/div, 5V DC OFFSET
C: INDUCTOR CURRENT, 1A/div
Figure 4. Continuous-Conduction Mode, Heavy-Load-Current
Waveform
