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MAX1974EUB+

P1-P3P4-P6P7-P9P10-P12P13-P15
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
Features
♦ Tiny Circuit Footprint of 0.19in
2
♦ Ultra-Low Circuit Height of 1.8mm
♦ 4.7µF Ceramic Input and Output Capacitors
♦ 2.6V to 5.5V Input Voltage
♦ 1A Output Current
♦ 1% Accurate
♦ Built-In ±4% Logic-Controlled Voltage Margining
(MAX1973)
♦ Preset 1V, 1.5V, 1.8V, 2.5V, or 0.75V to V
IN
Adjustable Output
♦ Fixed-Frequency PWM Current-Mode Operation
♦ 1.4MHz Switching Frequency, Operate Outside
DSL Band
♦ 100% Duty-Cycle Dropout Capability
♦ Small External Components
MAX1973/MAX1974
Smallest 1A, 1.4MHz Step-Down Regulators
________________________________________________________________ Maxim Integrated Products 1
1
2
3
4
5
10
9
8
7
6
CTL1
IN
LX
PGNDSS
FB
COMP
FBSEL
MAX1973
µMAX
TOP VIEW
CTL2GND
1
2
3
4
5
10
9
8
7
6
ON
IN
LX
PGNDSS
FB
COMP
FBSEL
MAX1974
µMAX
POKGND
Pin Configurations
Ordering Information
MAX1973
IN
COMP
FBSEL
SS
GND
LX
FB
CTL1
CTL2
PGND
INPUT
2.6V TO 5.5V
MAX1974 OUTPUT DOWN TO 0.75V
VOLTAGE
MARGINING
ON/OFF
OUTPUT
1.25V TO V
IN
1A
Typical Operating Circuit
19-2547; Rev 0; 7/02
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
PART TEMP RANGE PIN-PACKAGE
MAX1973EUB -40°C to +85°C 10 µMAX
MAX1974EUB -40°C to +85°C 10 µMAX
Selector Guide appears at end of data sheet.
MAX1973/MAX1974
Smallest 1A, 1.4MHz Step-Down Regulators
2 _______________________________________________________________________________________
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, POK, CTL1, CTL2, FBSEL, ON to GND ..............-0.3V to +6V
COMP, FB, SS to GND ................................-0.3V to (V
IN
+ 0.3V)
PGND to GND .......................................................-0.3V to +0.3V
LX Current (Note 1) ...............................................-2.4A to +2.4A
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) .......... 444mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
ELECTRICAL CHARACTERISTICS
(V
IN
= V
CTL_
= 3.3V, FB = OUT, T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER CONDITIONS
MIN TYP MAX UNITS
IN
IN Voltage Range 2.6 5.5 V
IN Undervoltage Lockout
Threshold
Rising and falling, hysteresis is 25mV (typ) 2.2
2.35
2.5 V
Supply Current Switching with no load 4.0 7.5 mA
Supply Current in Dropout V
OUT
set for 3.6V 3 5 mA
Shutdown Supply Current V
IN
= 5.5V 0.1 10 µA
FB
MAX1973
1.25
V
IN
Output Voltage Range
MAX1974
0.75
V
IN
V
FBSEL not connected
1.2375 1.25 1.2625
FBSEL = GND
1.7820
1.8
1.8180
MAX1973
FBSEL = IN
2.4750
2.5
2.5250
FBSEL not connected
0.7425 0.75 0.7575
FBSEL = GND
0.99 1.00 1.01
FB Regulation Voltage
MAX1974
FBSEL = IN
1.485 1.500 1.515
V
FB Regulation Voltage
Positive Voltage Margining
MAX1973, CTL1 = GND, CTL2 = IN +3 +4 +5 %
FB Regulation Voltage
Negative Voltage Margining
MAX1973, CTL1 = IN, CTL2 = GND -3 -4 -5 %
FB Input Resistance to GND in
Preset Output Modes
10 30 70 kΩ
FB Input Bias Current FBSEL not connected
-0.1 0.01 +0.1
µA
SS (REFERENCE OUTPUT)
MAX1974
0.75
SS Voltage
MAX1973
1.25
V
Note 1: LX has internal clamp diodes to IN and PGND. Applications that forward bias these diodes should take care not to exceed
the IC package power dissipation limit.
MAX1973/MAX1974
Smallest 1A, 1.4MHz Step-Down Regulators
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
CTL_
= 3.3V, FB = OUT, T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER CONDITIONS
MIN
TYP
MAX
SS Source Current -25 -20 -15 µA
SS Sink Current 10 20 35 µA
SS to GND Resistance in
Shutdown
540
100
Ω
FBSEL
Low Input Threshold 0.3 V
High Input Threshold
V
IN
-
0.3
V
Input Bias Current FBSEL = GND or IN, V
IN
= 5.5V -20 10
+20
µA
COMP
Transconductance from FB to
COMP
40 60 80 µS
COMP to GND Resistance in
Shutdown
540
100
Ω
Clamp Voltage Low 0.6 0.9 1.2 V
Clamp Voltage High
1.35 1.75 2.15
V
LX
On-Resistance High V
IN
= 3.3V
0.23 0.46
Ω
On-Resistance Low V
IN
= 3.3V
0.16 0.32
Ω
Current-Sense Transresistance
0.275 0.335 0.425
V/A
Positive Current-Limit Threshold
1.1 1.6
1.75
A
Negative Current-Limit Threshold
-1.2 -0.8 -0.4
A
V
LX
= V
IN
= 5.5V 20
LX Shutdown Leakage Current
LX = GND, V
IN
= 5.5V -20
µA
Switching Frequency 1.2 1.4 1.6
CTL1, CTL2 (MAX1973), ON (MAX1974)
Logic-Low Input Threshold 0.6 V
Logic-High Input Threshold 1.6 V
Logic Input Current -1 +1 µA
POK (MAX1974 only)
Output Low Voltage POK sinking 1mA 10
100
mV
Rising 90
92.5
95
Output Valid Threshold for POK
Percentage of nominal
regulation voltage
Falling 88 90 92
%
P1-P3P4-P6P7-P9P10-P12P13-P15

MAX1974EUB+

Mfr. #:
Buy MAX1974EUB+
Manufacturer:
Maxim Integrated
Description:
Switching Voltage Regulators 1A 1.4MHz Step-Down Regulator
Lifecycle:
New from this manufacturer.
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