MAX668EUB ,1.8V to 28V Input / PWM Step-Up Controllers in MAXELECTRICAL CHARACTERISTICS(V = LDO = +5V, R = 200kΩ, T = 0°C to +85°C, unless otherwise noted. Typi ..
MAX668EUB ,1.8V to 28V Input / PWM Step-Up Controllers in MAXFeaturesThe MAX668/MAX669 constant-frequency, pulse-width-' 1.8V Minimum Start-Up Voltage (MAX669)m ..
MAX668EUB ,1.8V to 28V Input / PWM Step-Up Controllers in MAXApplicationsoperates in PWM mode at medium and heavy loads forlowest noise and optimum efficiency, ..
MAX668EUB+ ,1.8V to 28V Input, PWM Step-Up Controllers in µMAXApplications100mV current-sense voltage as well as with Maxim’s proprietary Idle Mode™ control sche ..
MAX668EUB+T ,1.8V to 28V Input, PWM Step-Up Controllers in µMAXElectrical Characteristics (continued)(V = V = +5V, R = 200kΩ, T = 0°C to +85°C, unless otherwise n ..
MAX6690MEE ,2C Accurate Remote/Local Temperature Sensor with SMBus Serial InterfaceMAX669019-2190; Rev 0; 10/012°C Accurate Remote/Local TemperatureSensor with SMBus Serial Interface
MB3771PF-G-BND-JNE1 , ASSP For power supply applications BIPOLAR Power Supply Monitor
MB3771PS ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
MB3771PS ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
MB3773 ,Power Supply Monitor with Watch-Dog TimerFUJITSU SEMICONDUCTORDS04-27401-4EDATA SHEETASSPPower Supply Monitor with Watch-Dog TimerMB3773n DE ..
MB3775 ,SWITCHING REGULATOR CONTROLLERFUJITSU SEMICONDUCTORDS04-27204-3EDATA SHEETASSPSWITCHING REGULATOR CONTROLLERMB3775LOW VOLTAGE DUA ..
MB3775PF , SWITCHING REGULATOR CONTROLLER
MAX668EUB-MAX669EUB
1.8V to 28V Input / PWM Step-Up Controllers in MAX
General DescriptionThe MAX668/MAX669 constant-frequency, pulse-width-
modulating (PWM), current-mode DC-DC controllers are
designed for a wide range of DC-DC conversion applica-
tions including step-up, SEPIC, flyback, and isolated-
output configurations. Power levels of 20W or more can
be controlled with conversion efficiencies of over 90%.
The 1.8V to 28V input voltage range supports a wide
range of battery and AC-powered inputs. An advanced
BiCMOS design features low operating current (220µA),
adjustable operating frequency (100kHz to 500kHz),
soft-start, and a SYNC input allowing the MAX668/
MAX669 oscillator to be locked to an external clock.
DC-DC conversion efficiency is optimized with a low
100mV current-sense voltage as well as with Maxim’s
proprietary Idle Mode™ control scheme. The controller
operates in PWM mode at medium and heavy loads for
lowest noise and optimum efficiency, then pulses only as
needed (with reduced inductor current) to reduce oper-
ating current and maximize efficiency under light loads.
A logic-level shutdown input is also included, reducing
supply current to 3.5µA.
The MAX669, optimized for low input voltages with a
guaranteed start-up voltage of 1.8V, requires boot-
strapped operation (IC powered from boosted output). It
supports output voltages up to 28V. The MAX668 oper-
ates with inputs as low as 3V and can be connected in
either a bootstrapped or non-bootstrapped (IC powered
from input supply or other source) configuration. When
not bootstrapped, it has no restriction on output voltage.
Both ICs are available in an extremely compact 10-pin
µMAX package.
Features1.8V Minimum Start-Up Voltage (MAX669)Wide Input Voltage Range (1.8V to 28V)Tiny 10-Pin µMAX PackageCurrent-Mode PWM and Idle Mode™OperationEfficiency over 90%Adjustable 100kHz to 500kHz Oscillator or
SYNC Input 220µA Quiescent CurrentLogic-Level ShutdownSoft-Start
ApplicationsCellular Telephones
Telecom Hardware
LANs and Network Systems
POS Systems
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
Ordering Information
Typical Operating Circuit
Pin Configuration
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= LDO= +5V, ROSC= 200kΩ, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
VCCto GND ..........................................................-0.3V to +30V
PGND to GND....................................................................±0.3V
SYNC/SHDNto GND.............................................-0.3V to +30V
EXT, REF to GND.....................................-0.3V to (VLDO+ 0.3V)
LDO, FREQ, FB, CS+ to GND................................-0.3V to +6V
LDO Output Current...........................................-1mA to +20mA
REF Output Current..............................................-1mA to +1mA
LDO Short Circuit to GND.........................................Momentary
REF Short Circuit to GND..........................................Continuous
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,10sec)..............................+300°C
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
ELECTRICAL CHARACTERISTICS (continued)(VCC= LDO = +5V, ROSC= 200kΩ, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
ELECTRICAL CHARACTERISTICS(VCC= LDO = +5V, ROSC= 200kΩ, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
ELECTRICAL CHARACTERISTICS (continued)(VCC= LDO = +5V, ROSC= 200kΩ, TA= -40°C to +85°C, unless otherwise noted.)
Note 1:This is the VCCcurrent consumed when active but not switching. Does not include gate-drive current.
Note 2:Limits at TA= -40°C are guaranteed by design.
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
Typical Operating Characteristics(Circuits of Figures 2, 3, 4, and 5; TA= +25°C; unless otherwise noted.)
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
Typical Operating Characteristics (continued)(Circuits of Figures 2, 3, 4, and 5; TA= +25°C; unless otherwise noted.)
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX ypical Operating Characteristics (continued)(Circuits of Figures 2, 3, 4, and 5; TA= +25°C; unless otherwise noted.)
Detailed DescriptionThe MAX668/MAX669 current-mode PWM controllers
operate in a wide range of DC-DC conversion applica-
tions, including boost, SEPIC, flyback, and isolated out-
put configurations. Optimum conversion efficiency is
maintained over a wide range of loads by employing
both PWM operation and Maxim’s proprietary Idle
Mode control to minimize operating current at light
loads. Other features include shutdown, adjustable
internal operating frequency or synchronization to an
external clock, soft start, adjustable current limit, and a
wide (1.8V to 28V) input range.
MAX668 vs. MAX669 DifferencesDifferences between the MAX668 and MAX669 relate
to their use in bootstrapped or non-bootstrapped cir-
cuits (Table 1). The MAX668 operates with inputs as
low as 3V and can be connected in eithera boot-
strapped or non-bootstrapped (IC powered from input
supply or other source) configuration. When not boot-
strapped, the MAX668 has no restriction on output volt-
age. When bootstrapped, the output cannot exceed
28V.
The MAX669 is optimized for low input voltages (down
to 1.8V) and requiresbootstrapped operation (IC pow-
ered from VOUT) with output voltages no greater than
28V. Bootstrapping is required because the MAX669
does not have undervoltage lockout, but instead drives
EXT with an open-loop, 50% duty-cycle start-up oscilla-
tor when LDO is below 2.5V. It switches to closed-loop
operation only when LDO exceeds 2.5V. If a non-boot-
strapped connection is used with the MAX669 and if
VCC(the input voltage) remains below 2.7V, the output
voltage will soar above the regulation point. Table 2
recommends the appropriate device for each biasing
option.
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
Pin Description
PWM ControllerThe heart of the MAX668/MAX669 current-mode PWM
controller is a BiCMOS multi-input comparator that
simultaneously processes the output-error signal, the
current-sense signal, and a slope-compensation ramp
(Figure 1). The main PWM comparator is direct sum-
ming, lacking a traditional error amplifier and its associ-
ated phase shift. The direct summing configuration
approaches ideal cycle-by-cycle control over the out-
put voltage since there is no conventional error amp in
the feedback path.
In PWM mode, the controller uses fixed-frequency, cur-
rent-mode operation where the duty ratio is set by the
input/output voltage ratio (duty ratio = (VOUT- VIN) / VIN
in the boost configuration). The current-mode feedback
loop regulates peak inductor current as a function of
the output error signal.
At light loads the controller enters Idle Mode. During
Idle Mode, switching pulses are provided only as need-
ed to service the load, and operating current is mini-
mized to provide best light-load efficiency. The
minimum-current comparator threshold is 15mV, or 15%
of the full-load value (IMAX) of 100mV. When the con-
troller is synchronized to an external clock, Idle Mode
occurs only at very light loads.
Bootstrapped/Non-Bootstrapped Operation
Low-Dropout Regulator (LDO)Several IC biasing options, including bootstrapped and
non-bootstrapped operation, are made possible by an
on-chip, low-dropout 5V regulator. The regulator input is
at VCC, while its output is at LDO. All MAX668/MAX669
functions, including EXT, are internally powered from
LDO. The VCC-to-LDO dropout voltage is typically
200mV (300mV max at 12mA), so that when VCCis less
than 5.2V, LDO is typically VCC - 200mV. When LDO is
in dropout, the MAX668/MAX669 still operate with VCC
as low as 3V (as long as LDO exceeds 2.7V), but with
reduced amplitude FET drive at EXT. The maximum
VCCinput voltage is 28V.
LDO can supply up to 12mA to power the IC, supply
gate charge through EXT to the external FET, and sup-
ply small external loads. When driving particularly large
FETs at high switching rates, little or no LDO current
may be available for external loads. For example, when
switched at 500kHz, a large FET with 20nC gate charge
requires 20nC x 500kHz, or 10mA.
VCCand LDO allow a variety of biasing connections to
optimize efficiency, circuit quiescent current, and full-
load start-up behavior for different input and output
voltage ranges. Connections are shown in Figures 2, 3,
4, and 5. The characteristics of each are outlined in
Table 1.
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
