19-1618; Rev 0; 4/00
50mA Regulated Step-Down Charge Pump
for 1.8V or 1.9V Logic
General Description
The MAX1730 regulated step-down charge pump gen-
erates up to 50mA at fixed output voltages of 1.8V or
1.9V from an input voltage in the 2.7V to 5.5V range.
Specifically designed to provide high-efficiency logic
supplies in applications that demand a compact
design, the MAX1730 employs fractional conversion
techniques to provide efficiency exceeding that of a lin-
ear regulator.
The MAX1730 operates at up to 2MHz, permitting the
use of small 0.22µF flying capacitors while maintaining
low 75µA quiescent supply current. Proprietary soft-
start circuitry prevents excessive current from being
drawn from the supply during startup, making the
MAX1730 compatible with higher impedance sources
such as alkaline and lithium-ion cells.
The MAX1730 is available in a space-saving 10-pin
µMAX package that is only 1.09mm high and occupies
one-half the area of an 8-pin SO.
o
> 85% Peak Efficiency
o
50mA Guaranteed Output Current
o
Dual-Mode 1.8V or 1.9V Output
o
±3% Output Voltage Accuracy
o
Up to 2MHz Operating Frequency
o
Small 0.22µF Capacitors
o
No Inductor Required
o
2.7V to 5.5V Input Voltage Range
o
Output Disconnects from Input in Shutdown Mode
o
Small 10-Pin µMAX Package (1.09mm max height)
Features
MAX1730
Applications
Low-Voltage Logic Supplies
Wireless Handsets
PDAs
PC Cards
Hand-Held Instruments
PART
MAX1730EUB
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
10 µMAX
Typical Operating Circuit
INPUT
2.7V TO 5.5V
1µF
Pin Configuration
TOP VIEW
FB
1
IN
OUTPUT
1.8V OR 1.9V, UP TO 50mA
OUT
4.7µF
10
IN
9
OUT
C2P
C2N
PGND
SHDN
C1P
C1N
GND
2
3
4
5
SHDN
MAX1730
8
7
6
MAX1730
C1P
0.22µF
C1N
FB
C2N
GND PGND
C2P
0.22µF
µMAX
________________________________________________________________
Maxim Integrated Products
1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
50mA Regulated Step-Down Charge Pump
for 1.8V or 1.9V Logic
MAX1730
ABSOLUTE MAXIMUM RATINGS
IN, OUT,
SHDN,
FB to GND .....................................-0.3V to +6V
C1P, C1N, C2P, C2N to GND ......................-0.3V to (V
IN
+ 0.3V)
GND to PGND.....................................................................±0.3V
Output Short-Circuit Duration ........................................Indefinite
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
Junction Temperature ......................................................+150°C
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature Range (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.
ELECTRICAL CHARACTERISTICS
(V
IN
= +3.6V, FB = GND,
SHDN
= IN,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Input Voltage Range
Input Undervoltage Lockout
Output Voltage
Output Leakage Current
No-Load Supply Current
Shutdown Supply Current
Output Short-Circuit Current
Oscillator Frequency
Thermal Shutdown Threshold
Thermal Shutdown Threshold
Hysteresis
V
IN
Transition Voltage
(V
IN
Rising)
Startup Timer
SHDN
Logic Input High Voltage
SHDN
Logic Input Low Voltage
Shutdown Logic Input Current
V
IH
V
IL
I
SHDN
V
IN
= 2.7V to 5.5V
V
IN
= 2.7V to 5.5V
SHDN
= IN or GND
-1
1.4
0.6
1
FB = GND
From 1:1 to 2:3
From 2:3 to 1:2
3.1
4.00
V
OUT
SYMBOL
V
IN
Falling edge (100mV hysteresis)
V
IN
= 2.7V to 5.5V,
I
OUT
= 0 to 50mA
FB = GND
FB = IN
CONDITIONS
MIN
2.7
2.3
1.746
1.843
1.80
1.90
1
75
1
45
1.5
2.0
150
15
3.2
4.12
4.1
3.35
4.30
TYP
MAX
5.5
2.6
1.854
1.957
5
150
5
125
2.5
UNITS
V
V
V
µA
µA
µA
mA
MHz
°C
°C
V
ms
V
V
µA
OUT forced to 1.8V, V
IN
= 1.8V to 5.5V,
SHDN
= GND
SHDN
= IN
V
IN
= 4.2V,
SHDN
= GND, V
OUT
= 1.8V or GND
V
OUT
= GND
2
_______________________________________________________________________________________
50mA Regulated Step-Down Charge Pump
for 1.8V or 1.9V Logic
ELECTRICAL CHARACTERISTICS
(V
IN
= +3.6V, FB = GND,
SHDN
= IN,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
Input Voltage Range
Input Undervoltage Lockout
Output Voltage
Output Leakage Current
No-Load Supply Current
Shutdown Supply Current
Output Short-Circuit Current
Oscillator Frequency
V
IN
Transition Voltage
(V
IN
Rising)
SHDN
Logic Input High Voltage
SHDN
Logic Input Low Voltage
Shutdown Logic Input Current
V
IH
V
IL
I
SHDN
f
FB = GND
V
IN
= 2.7V to 5.5V
V
IN
= 2.7V to 5.5V
SHDN
= IN or GND
-1
From 1:1 to 2:3
From 2:3 to 1:2
V
OUT
SYMBOL
V
IN
Falling edge (100mV hysteresis)
V
IN
= 2.7V to 5.5V,
I
OUT
= 0 to 50mA
FB = GND
FB = IN
CONDITIONS
MIN
2.7
2.3
1.746
1.843
MAX
5.5
2.6
1.854
1.957
5
150
5
125
1.5
3.1
4.00
1.4
0.6
1
2.5
3.35
4.30
UNITS
V
V
V
µA
µA
µA
mA
MHz
V
V
V
µA
MAX1730
OUT forced to 1.8V, V
IN
= 1.8V to 5.5V,
SHDN
= GND
SHDN
= IN
V
IN
= 4.2V,
SHDN
= GND
V
OUT
= GND
Note 1:
Specifications to -40°C are guaranteed by design, not production tested.
_______________________________________________________________________________________
3
50mA Regulated Step-Down Charge Pump
for 1.8V or 1.9V Logic
MAX1730
Typical Operating Characteristics
(V
IN
= +3.6V, FB = GND,
SHDN
= IN, C
IN
= 1µF, C1 = C2 = 0.22µF, C
OUT
= 4.7µF, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY
vs. OUTPUT CURRENT
MAX1730 TOC01
EFFICIENCY vs. INPUT VOLTAGE
MAX1730 TOC02
EFFICIENCY vs. INPUT VOLTAGE
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
I
OUT
= 50mA
MAX1730 TOC02
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
10
100
V
IN
= 2.7V
V
IN
= 5.0V
V
IN
= 3.6V
V
IN
= 3.3V
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
I
OUT
= 25mA
100
1000
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT CURRENT vs. INPUT VOLTAGE
MAX1730 TOC04
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1730 TOC05
OUTPUT VOLTAGE vs. INPUT VOLTAGE
1.8
1.6
OUTPUT VOLTAGE (V)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
I
OUT
= 0 to 50mA
0
1
2
3
4
5
6
MAX1730 TOC06
70
60
INPUT CURRENT (µA)
50
40
30
20
10
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
SHUTDOWN CURRENT
NO-LOAD
SUPPLY CURRENT
1.85
V
IN
= 5.0V
V
IN
= 3.3V
1.81
V
IN
= 2.7V
2.0
1.83
OUTPUT VOLTAGE (V)
1.79
1.77
1.75
5.5
0.1
1
10
100
1000
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
0
INPUT VOLTAGE (V)
4
_______________________________________________________________________________________
50mA Regulated Step-Down Charge Pump
for 1.8V or 1.9V Logic
Typical Operating Characteristics (continued)
(V
IN
= +3.6V, FB = GND,
SHDN
= IN, C
IN
= 1µF, C1 = C2 = 0.22µF, C
OUT
= 4.7µF, T
A
= +25°C, unless otherwise noted.)
MAX1730
LINE-TRANSIENT RESPONSE
MAX1730 TOC07
LOAD-TRANSIENT RESPONSE
MAX1730 TOC08
STARTUP AND SHUTDOWN RESPONSE
MAX1730 TOC09
4V
V
IN
3V
50mA
I
OUT
5mA
V
O
1V/div
I
IN
50mA/div
R
L
= 72Ω
V
OUT
AC-COUPLED
50mV/div
V
OUT
AC-COUPLED
20mV/div
V
SHDN
5V/div
10µs/div
10µs/div
100µs/div
Pin Description
PIN
1
NAME
FB
FUNCTION
Feedback Input. Connect FB to GND for a 1.8V output. Connect FB to IN for a 1.9V output. Do not leave FB
unconnected.
Active-Low Shutdown Input. Connect to logic control or to IN for normal operation. OUT disconnects from the
input in shutdown and goes to high impedance.
C1 Flying Capacitor Positive Connection
C1 Flying Capacitor Negative Connection
Ground
Power Ground
C2 Flying Capacitor Negative Connection
C2 Flying Capacitor Positive Connection
Output. Bypass to GND with a 4.7µF or greater capacitor.
Input Supply. Connect to a +2.7V to +5.5V supply. Bypass to GND with a 1µF ceramic capacitor as close to
the IC as possible.
2
3
4
5
6
7
8
9
10
SHDN
C1P
C1N
GND
PGND
C2N
C2P
OUT
IN
_______________________________________________________________________________________
5
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