View MAX1730EUB_4122269.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

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 generates 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 linear regulator. The MAX1730 operates at up to 2MHz, permitting the use of small 0.22F flying capacitors while maintaining low 75A quiescent supply current. Proprietary softstart 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 MAX 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 0.22F 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 MAX 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 -40C to +85C PIN-PACKAGE 10 MAX
Typical Operating Circuit
INPUT 2.7V TO 5.5V 1F
Pin Configuration
TOP VIEW
FB 1
IN OUTPUT 1.8V OR 1.9V, UP TO 50mA OUT 4.7F
10 IN 9 OUT C2P C2N PGND
SHDN C1P C1N GND
2 3 4 5
SHDN
MAX1730
8 7 6
MAX1730
C1P 0.22F C1N FB C2N GND PGND C2P 0.22F
MAX
________________________________________________________________ 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 (VIN + 0.3V) GND to PGND.....................................................................0.3V Output Short-Circuit Duration ........................................Indefinite Continuous Power Dissipation (TA = +70C) 10-Pin MAX (derate 5.6mW/C above +70C) ...........444mW Junction Temperature ......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature Range (soldering, 10s)......................+300C
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
(VIN = +3.6V, FB = GND, SHDN = IN, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) 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 VIN Transition Voltage (VIN Rising) Startup Timer SHDN Logic Input High Voltage SHDN Logic Input Low Voltage Shutdown Logic Input Current VIH VIL ISHDN VIN = 2.7V to 5.5V VIN = 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 VOUT SYMBOL VIN Falling edge (100mV hysteresis) VIN = 2.7V to 5.5V, IOUT = 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 A A A mA MHz C C V ms V V A
OUT forced to 1.8V, VIN = 1.8V to 5.5V, SHDN = GND SHDN = IN VIN = 4.2V, SHDN = GND, VOUT = 1.8V or GND VOUT = GND
2
_______________________________________________________________________________________
50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic
ELECTRICAL CHARACTERISTICS
(VIN = +3.6V, FB = GND, SHDN = IN, TA = -40C to +85C, 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 VIN Transition Voltage (VIN Rising) SHDN Logic Input High Voltage SHDN Logic Input Low Voltage Shutdown Logic Input Current VIH VIL ISHDN f FB = GND VIN = 2.7V to 5.5V VIN = 2.7V to 5.5V SHDN = IN or GND -1 From 1:1 to 2:3 From 2:3 to 1:2 VOUT SYMBOL VIN Falling edge (100mV hysteresis) VIN = 2.7V to 5.5V, IOUT = 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 A A A mA MHz V V V A
MAX1730
OUT forced to 1.8V, VIN = 1.8V to 5.5V, SHDN = GND SHDN = IN VIN = 4.2V, SHDN = GND VOUT = GND
Note 1: Specifications to -40C 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
(VIN = +3.6V, FB = GND, SHDN = IN, CIN = 1F, C1 = C2 = 0.22F, COUT = 4.7F, TA = +25C, 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 IOUT = 50mA
MAX1730 TOC02
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.1 1 10 100 VIN = 2.7V VIN = 5.0V VIN = 3.6V VIN = 3.3V
100 95 90 EFFICIENCY (%) 85 80 75 70 65 60 55 50 IOUT = 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 IOUT = 0 to 50mA 0 1 2 3 4 5 6
MAX1730 TOC06
70 60 INPUT CURRENT (A) 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 VIN = 5.0V VIN = 3.3V 1.81 VIN = 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)
(VIN = +3.6V, FB = GND, SHDN = IN, CIN = 1F, C1 = C2 = 0.22F, COUT = 4.7F, TA = +25C, unless otherwise noted.)
MAX1730
LINE-TRANSIENT RESPONSE
MAX1730 TOC07
LOAD-TRANSIENT RESPONSE
MAX1730 TOC08
STARTUP AND SHUTDOWN RESPONSE
MAX1730 TOC09
4V VIN 3V
50mA IOUT 5mA VO 1V/div IIN 50mA/div
RL = 72
VOUT AC-COUPLED 50mV/div
VOUT AC-COUPLED 20mV/div VSHDN 5V/div
10s/div
10s/div
100s/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 4.7F or greater capacitor. Input Supply. Connect to a +2.7V to +5.5V supply. Bypass to GND with a 1F 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
50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic MAX1730
Functional Diagram
OUT FB FB CONTROL C1P DRIVERS VREF + C1N
OSCILLATOR
MAX1730
SWITCH ARRAY C2P CONTROL LOGIC C2N SHUTDOWN SHDN PGND
GND
IN
Detailed Description
The MAX1730 step-down charge pump automatically switches between charge pump configurations (Figures 1, 2, and 3) and utilizes pulse-skipping pulse-frequency modulation (PFM) to provide a regulated output voltage with high efficiency. The output voltage is pin-selectable to 1.8V or 1.9V. The MAX1730 accepts inputs between 2.7V and 5.5V and guarantees up to 50mA output current.
Figure 2 shows the 3:2 charge-pump configuration. C1 and C2 charge in parallel between IN and OUT during the first phase. In the second phase, C1 and C2 connect in series between OUT and GND. Figure 3 shows the 2:1 charge-pump configuration. C1 and C2 charge in parallel between IN and OUT during the first phase. In the second phase, C1 and C2 connect in parallel between OUT and GND.
Charge-Pump Configurations
Charge pumps work by passing energy through capacitors. They generally work in two phases. In the first phase, the input source charges the flying capacitors. The input capacitor helps reduce the source's input impedance. In the second phase, the switching capacitors transfer their charge to the output as needed. Figure 1 shows the 1:1 charge-pump configuration. C1 and C2 charge in parallel between IN and GND during the first phase. In the second phase, C1 and C2 connect in parallel between OUT and GND.
Pulse-Skipping PFM and Mode Transitions
In the MAX1730, pulse-skipping PFM mode pauses the oscillator when the output is in regulation. Using the 2:1 charge-pump configuration as an example, when the output is set to half the input, the switching frequency is near the oscillator frequency. However, for outputs below half the input, switching pauses once the desired output level is achieved. With no output current, the device switches occasionally. With higher levels of current, the switching frequency increases to supply the load.
6
_______________________________________________________________________________________
50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic MAX1730
VIN VOUT = VIN CIN COUT
C1
C2
NOTE: SWITCH STATES SET FOR STAGE 1. ALL SWITCHES REVERSE STATE FOR STAGE 2.
Figure 1. 1:1 Capacitor Configuration
VIN CIN
VIN CIN
C1
C2 C1 C2
VOUT = 2 VIN 3 COUT COUT
VOUT = 1 VIN 2
NOTE: SWITCH STATES SET FOR STAGE 1. ALL SWITCHES REVERSE STATE FOR STAGE 2.
NOTE: SWITCH STATES SET FOR STAGE 1. ALL SWITCHES REVERSE STATE FOR STAGE 2.
Figure 2. 3:2 Capacitor Configuration
Figure 3. 2:1 Capacitor Configuration
To maximize efficiency, the MAX1730 automatically switches between charge-pump configurations (Figures 1, 2, and 3). Efficiency is greatest when the IN/OUT voltage ratio is close to the voltage ratio of the selected capacitor configuration and decreases for output voltages lower than the divider ratio. To choose between configurations, the MAX1730 senses the input voltage and the output voltage. The MAX1730 uses a control scheme with hysteresis to prevent oscillation between capacitor configurations.
Applications Information
Setting the Output Voltage
For an output voltage of 1.8V, connect FB to GND. For an output voltage of 1.9V, connect FB to IN.
_______________________________________________________________________________________
7
50mA Regulated Step-Down Charge Pump for 1.8V or 1.9V Logic MAX1730
Shutdown
The MAX1730 features an active-low shutdown pin (SHDN) to decrease supply current to below 5A. When in shutdown, the output disconnects from the input and OUT goes to high impedance.
Layout Considerations
The MAX1730's high-frequency operation demands careful layout. All components should be placed as close to the IC as possible, with priority going to CIN, C1, and C2. Traces should be kept short, wide, and as straight as possible. Connect PGND and GND together with a low-impedance ground plane.
Capacitor Selection
The input capacitor provides the charge pump with a lowimpedance supply. For most applications, a 1F ceramic capacitor is adequate. Lower-value capacitors and those with higher ESR may be inadequate for proper operation and may result in lower output current capability and higher output ripple. To reduce the output voltage ripple, the value of the output capacitor should exceed that of the flying capacitors (C1 + C2) by 10:1 or more. Values for C1 and C2 between 0.22F and 0.47F are recommended for most applications. Use ceramic capacitors to increase maximum output current and improve efficiency.
Chip Information
TRANSISTOR COUNT: 2295
Package Information
10LUMAX.EPS
Note: The MAX1730 does not have an exposed pad.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
This datasheet has been download from: www..com Datasheets for electronics components.

▲Up To Search▲

Price & Availability of MAX1730EUB

	To Download MAX1730EUB Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .