MAX1973 Datasheet, PDF (1/15 Pages) Maxim Integrated Products – Smallest 1A, 1.4MHz Step-Down Regulators

19-2547; Rev 0; 7/02
Smallest 1A, 1.4MHz Step-Down Regulators
General Description
The MAX1973/MAX1974 are constant-frequency
1.4MHz pulse-width-modulated (PWM) current-mode
step-down regulators. The output voltage can be set as
low as 0.75V using an external voltage-divider, or it can
be set to preset outputs of 1V, 1.5V (MAX1974), 1.8V,
or 2.5V (MAX1973) without requiring external resistors.
The MAX1973 also includes a voltage-margining fea-
ture that offsets the output voltage up or down 4% to
facilitate board-level production testing.
A fixed 1.4MHz operating frequency ensures operation
outside the DSL frequency band, provides fast transient
response, and allows the use of small external compo-
nents. Only 4.7µF input and output ceramic capacitors
are needed for 1A applications. Forced PWM operation
ensures a constant switching frequency over all load
conditions.
Output voltage accuracy is ±1% over load, line, and
temperature operating ranges. The MAX1973 features
voltage margining; the MAX1974 provides a POK out-
put to indicate when the output has reached 90% of its
nominal regulation voltage. Both devices are available
in small 10-pin µMAX packages.
Applications
Network Equipment
Cellular Base Stations
DSL and Wireless Modems/Routers
Optical Modules
Central-Office DSL and Telecom
DSP/ASIC Core and IO supplies
Selector Guide appears at end of data sheet.
Typical Operating Circuit
INPUT
2.6V TO 5.5V
IN
LX
COMP
FB
FBSEL MAX1973
CTL1
SS
CTL2
GND
PGND
OUTPUT
1.25V TO V_IN
1A
VOLTAGE
MARGINING
ON/OFF
MAX1974 OUTPUT DOWN TO 0.75V
Features
o Tiny Circuit Footprint of 0.19in²
o Ultra-Low Circuit Height of 1.8mm
o 4.7µF Ceramic Input and Output Capacitors
o 2.6V to 5.5V Input Voltage
o 1A Output Current
o 1% Accurate
o Built-In ±4% Logic-Controlled Voltage Margining
(MAX1973)
o Preset 1V, 1.5V, 1.8V, 2.5V, or 0.75V to V_IN
Adjustable Output
o Fixed-Frequency PWM Current-Mode Operation
o 1.4MHz Switching Frequency, Operate Outside
DSL Band
o 100% Duty-Cycle Dropout Capability
o Small External Components
PART
MAX1973EUB
MAX1974EUB
Ordering Information
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
10 µMAX
Pin Configurations
TOP VIEW
FBSEL 1
COMP 2
FB 3
SS 4
GND 5
MAX1973
µMAX
10 CTL1
9 IN
8 LX
7 PGND
6 CTL2
FBSEL 1
COMP 2
FB 3
SS 4
GND 5
MAX1974
µMAX
10 ON
9 IN
8 LX
7 PGND
6 POK
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