Features: ` 97% Efficiency
` 4.2V to 30V Input Range
` 2.5V to 5.5V Dual Adjustable Outputs
` Selectable 3.3V and 5V Fixed or Adjustable Outputs (Dual Mode™)
` 12V Linear Regulator
` Adjustable Secondary Feedback (MAX8741)
` 5V/50mA Linear-Regulator Output
` Precision 2.5V Reference Output
` Programmable Power-Up Sequencing
` Power-Good (RESET) Output
` Output Overvoltage Protection
` Output Undervoltage Shutdown
` 333kHz/500kHz Low-Noise, Fixed-Frequency Operation
` Low-Dropout, 98% Duty-Factor Operation
` 2.5mW Typical Quiescent Power (12V Input,Both SMPSs On)
` 4A Typical Shutdown CurrentApplicationNotebook and Subnotebook Computers
PDAs and Mobile Communicators
Desktop CPU Local DC-DC ConvertersPinout
SpecificationsV+ to GND ...........................................................-0.3V to +36V
PGND to GND...................................................................±0.3V
VL to GND ..............................................................-0.3V to +6V
BST3, BST5 to GND ..............................................-0.3V to +36V
CSH3, CSH5 to GND................................................-0.3V to +6V
FB3 to GND..............................................-0.3V to (CSL3 + 0.3V)
FB5 to GND...............................................-0.3V to (CSL5 +0.3V)
LX3 to BST3............................................................-6V to +0.3V
LX5 to BST5............................................................-6V to +0.3V
REF, SYNC, SEQ, STEER, SKIP,
TIME/ON5, SECFB, RESET to GND ............-0.3V to (VL + 0.3V)
VDD to GND..........................................................-0.3V to +20V
RUN/ON3, SHDN to GND..............................-0.3V to (V+ + 0.3V)
12OUT to GND ..........................................-0.3V to (VDD + 0.3V)
DL3, DL5 to PGND........................................-0.3V to (VL + 0.3V)
DH3 to LX3 ..............................................-0.3V to (BST3 + 0.3V)
DH5 to LX5 ..............................................-0.3V to (BST5 + 0.3V)
VL, REF Short to GND ................................................Momentary
12OUT Short to GND..................................................Continuous
REF Current...........................................................+5mA to -1mA
VL Current.........................................................................+50mA
12OUT Current . .............................................................+200mA
VDD Shunt Current............................................................+15mA
Continuous Power Dissipation (TA = +70°C)
28-Pin SSOP (derate 9.52mW/°C above +70°C) ........762mW
32-Pin Thin QFN (derate 21.3mW/°C above +70°C)..1702mW
Operating Temperature Range .........................-40°C to +85°C
Storage Temperature Range ..........................-65°C to +160°C
Lead Temperature (soldering, 10s) ................................+300°C
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.
DescriptionThe MAX8741/MAX8742 are buck-topology, step-down,switch-mode, power-supply controllers that generate logic-supply voltages in battery-powered systems. These high-performance, dual/triple-output devices MAX8742 include onboard power-up sequencing, power-good signaling with delay, digital soft-start, secondary winding control, lowdropout circuitry, internal frequency-compensation networks,and automatic bootstrapping.
Up to 97% efficiency of MAX8742 is achieved through synchronous rectification and Maxim's proprietary Idle Mode™ control scheme. Efficiency is greater than 80% over a 1000:1 load-current range, which extends battery life in system suspend or standby mode. Excellent dynamic response corrects output load transients within five clock cycles.Strong 1A on-board gate drivers ensure fast external n-channel MOSFET switching.
These MAX8742 feature a logic-controlled and synchronizable,fixed-frequency, pulse-width-modulation (PWM) operating mode. This reduces noise and RF interference in sensitive mobile communications and pen-entry applications.Asserting the SKIP pin enables fixed-frequency mode, for lowest noise under all load conditions.
The MAX8741/MAX8742 include two PWM regulators,adjustable from 2.5V to 5.5V with fixed 5.0V and 3.3V modes. All these devices include secondary feedback regulation, and the MAX8742 contains a 12V/120mA linear regulator. The MAX8741 includes a secondary feedback input (SECFB), plus a control pin (STEER) that selects which PWM (3.3V or 5V) receives the secondary feedback signal. SECFB provides a method for adjusting the secondary winding voltage regulation point with an external resistor-divider, and is intended to aid in creating auxiliary voltages other than fixed 12V.
The MAX8741/MAX8742 contain internal output overvoltage-and undervoltage-protection features.
MAX8742 Data Sheet
