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19-2107; Rev 1; 8/02
Regulated 3.3V/5.0V Step-Up/Step-Down Charge Pump
General Description
The MAX1595 charge-pump regulator generates either 3.3V or 5V from a 1.8V to 5.5V input. The unique control architecture allows the regulator to step up or step down the input voltage to maintain output regulation. The 1MHz switching frequency, combined with a unique control scheme, allows the use of a ceramic capacitor as small as 1F for 125mA of output current. The complete regulator requires three external capacitors--no inductor is needed. The MAX1595 is specifically designed to serve as a high-power, highefficiency auxiliary supply in applications that demand a compact design. The MAX1595 is offered in spacesaving 8-pin MAX and high-power 12-pin thin QFN packages.
Features
o Ultra-Small: Requires Only Three Ceramic Capacitors o No Inductors Required o Up to 125mA Output Current o Regulated 3% Output Voltage o 1MHz Switching Frequency o 1.8V to 5.5V Input Voltage o 220A Quiescent Current o 0.1A Shutdown Current o Load Disconnect in Shutdown
MAX1595
Applications
White LED Power Flash Memory Supplies Battery-Powered Applications Miniature Equipment PCMCIA Cards 3.3V to 5V Local Conversion Applications Backup-Battery Boost Converters 3V to 5V GSM SIMM Cards
PART MAX1595EUA33 MAX1595ETC33 MAX1595EUA50 PART MAX1595EUA33 MAX1595ETC33 MAX1595EUA50 MAX1595ETC50
Ordering Information
TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 8 MAX 12 Thin QFN 8 MAX 12 Thin QFN
Selector Guide
VOUT * 3.3V 3.3V 5.0V TOP MARK -- AAAP --
Typical Operating Circuit
MAX1595ETC50 AAAM 5.0V *Contact factory for other fixed-output voltages from 2.7V to 5.0V.
Pin Configurations
CXN CXP
INPUT
MAX1595
IN OUT AOUT SHDN PGND GND OUTPUT
TOP VIEW
AOUT SHDN IN GND 1 2 3 4 8 OUT CXP CXN PGND
MAX1595
7 6 5
MAX
Pin Configurations continued at end of data sheet. Maxim Integrated Products 1
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Regulated 3.3V/5.0V Step-Up/Step-Down Charge Pump MAX1595
ABSOLUTE MAXIMUM RATINGS
IN, OUT, AOUT to GND............................................-0.3V to +6V SHDN to PGND ........................................................-0.3V to +6V PGND to GND .......................................................-0.3V to +0.3V CXN to PGND.....................-0.3V to (Lower of IN + 0.8V or 6.3V) CXP to GND ................................-0.8V to (Higher of OUT + 0.8V or IN + 0.8V but not greater than 6V) Continuous Output Current ...............................................150mA Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 4.5mW/C above +70C) ............362mW 12-Pin Thin QFN (derate 18.5mW/C above +70C)............................................................1481mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (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 = 2V for MAX1595_ _ _33, VIN = 3V for MAX1595_ _ _50, CIN = 1F, CX = 0.22F, COUT = 1F, TA = -40 to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Input Voltage Range Input Undervoltage Lockout Threshold Input Undervoltage Lockout Hysteresis 0 < ILOAD < 125mA, VIN = +3.0V Output Voltage VOUT TA = 0 to +85C TA = -40C to +85C 4.85 4.80 3.20 3.16 3.20 3.16 220 240 0.85 1.0 3.33 3.33 SYMBOL VIN CONDITIONS MIN 1.8 1.40 1.60 40 5.05 5.15 5.20 3.40 3.44 3.40 3.44 320 350 1.15 5 0.6 1.6 0.1 A MHz A V V A V TYP MAX 5.5 1.72 UNITS V V mV
0 < ILOAD < 75mA, VIN TA = 0 to +85C = +2.0V TA = -40C to +85C 0 < ILOAD < 30mA, VIN TA = 0 to +85C = +1.8V TA = -40C to +85C
No-Load Input Current Switching Frequency Shutdown Supply Current SHDN Input Voltage Low SHDN Input Voltage High SHDN Input Leakage Current
IQ fOSC I SHDN VINL VINH
VIN = +2.0V, MAX1595_ _ _33 VIN = +3.0V, MAX1595_ _ _50 ILOAD > 20mA, VOUT > VIN SHDN = 0, VIN = +5.5V, VOUT = 0 VIN = 2.0V to 5.5V VIN = 2.0V to 5.5V
Note 1: Specifications to -40C are guaranteed by design, not production tested.
2
_______________________________________________________________________________________
Regulated 3.3V/5.0V Step-Up/Step-Down Charge Pump
__________________________________________Typical Operating Characteristics
(Circuit of Figure 4, VIN = 2V for MAX1595_ _ _33, VIN = 3V for MAX1595_ _ _50, TA = +25C, unless otherwise noted.)
NO LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX1595 toc01
MAX1595
OUTPUT WAVEFORM
MAX1595 toc02
OUTPUT VOLTAGE vs. LOAD CURRENT
5.04 OUTPUT VOLTAGE (V) 5.02 5.00 4.98 4.96 4.94 4.92 VIN = 3V VIN = 3.3V VIN = 3.6V
MAX1595 toc03
10000
5.06
1000 SUPPLY CURRENT (A)
10
1 VOUT = 5V 0 1 2 3 4 5 6 VOUT = 5V
50mV/div
100
0.1 SUPPLY VOLTAGE (V)
4.90 200ns/div OUTPUT WAVEFORM. AC-COUPLED. VIN = 3.6V, ILOAD = 100mA, COUT = 1F 1 10 100 LOAD CURRENT (mA)
VOUT = 5V 1000
3V EFFICIENCY vs. LOAD CURRENT
90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 1 10 LOAD CURRENT (mA) 100 VIN = 2.4V VIN = 1.8V
MAX1595 toc04
5V EFFICIENCY vs. LOAD CURRENT
90 80
EFFICEINCY (%)
MAX1595 toc05
SHUTDOWN TIMING
MAX1595 toc06
100
100 VIN = 3V
5V
A
70 60 50 40 30 20 10 0 0.1 1 10 100 1000 LOAD CURRENT (mA) 100s/div A: OUTPUT VOLTAGE: RL = 100, 2V/div B: SHDN VOLTAGE: 2V/div VIN = 3.6V B VIN = 3.3V
LINE-TRANSIENT RESPONSE
MAX1595 toc07
LOAD-TRANSIENT RESPONSE
MAX1595 toc08
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
VOUT = 5V, ILOAD = 125mA
MAX1595 toc09
6 A A OUTPUT VOLTAGE (V) 4 3 2 1 COUT = 1F 0 2ms/div A: INPUT VOLTAGE: VIN = 3.1V TO 3.6V, 500mV/div B: OUTPUT VOLTAGE: ILOAD = 50mA, 100mV/div 200s/div A: LOAD CURRENT: ILOAD = 5mA to 95mA, 100mA/div B: OUTPUT VOLTAGE: AC-COUPLED 100mV/div 0 1 2 3 4 5 6 SUPPLY VOLTAGE (V) VOUT = 3.3V, ILOAD = 75mA 5
B
B
_______________________________________________________________________________________
3
Regulated 3.3V/5.0V Step-Up/Step-Down Charge Pump MAX1595
Pin Description
PIN MAX1595 MAX 1 2 3 4 5 6 7 8 MAX1595 THIN QFN 12 1 2, 3 4 5, 6 7, 8 9 10, 11 NAME FUNCTION
AOUT SHDN IN GND PGND CXN CXP OUT
Analog Power and Sense Input for Error Amplifier/Comparator. Connect to OUT at output filter capacitor. Shutdown Input. When SHDN = low, the device turns off; when SHDN = high, the device activates. In shutdown, OUT is disconnected from IN. Input Supply. Can range from 1.8V to 5.5V. Bypass to GND with a 1F capacitor. Ground Power Ground Negative Terminal of the Charge-Pump Transfer Capacitor Positive Terminal of the Charge-Pump Transfer Capacitor Output. Bypass to GND with output capacitor filter.
Detailed Description
The MAX1595 charge pump provides either a 3.3V or 5V regulated output. It delivers a maximum 125mA load current. In addition, to boost regulating from a lower supply, it is also capable of buck regulating from supplies that exceed the regulated output by a diode drop or more. Designed specifically for compact applications, a complete regulator circuit requires only three small external capacitors. An innovative control scheme provides constant frequency operation from medium to heavy loads, while smoothly transitioning to low-power mode at light loads to maintain optimum efficiency. In buck mode, switch S1 (in Figure 1) is switched continuously to IN, while switch S2 alternates between IN and OUT. An amount of charge proportional to the difference between the output voltage and the supply voltage is stored on CX, which gets transferred to the output when the regulation point is reached. Maximum output ripple is proportional to the difference between the supply voltage and the output voltage, as well as to the ratio of the transfer capacitor (CX) to the output capacitor (COUT). The MAX1595 consists of an error amplifier, a 1.23V bandgap reference, internal resistive feedback network, oscillator, high-current MOSFET switches, and shutdown and control logic. Figure 1 shows an idealized unregulated charge-pump voltage doubler. The oscillator runs at a 50% duty cycle. During one half of the period, the transfer capacitor (CX) charges to the input voltage. During the other half, the doubler transfers the sum of CX and input voltage to the output filter capacitor (COUT). Rather than doubling the input voltage, the MAX1595 provides a regulated output voltage of either 3.3V or 5.0V.
IN S1 CX
S2
OUT
CIN
COUT OSC
Figure 1. Unregulated Voltage Doubler
Shutdown
Driving SHDN low places the device in shutdown mode. The device draws 0.1A of supply current in this mode. When driven high, the MAX1595 enters a soft-start mode. Soft-start mode terminates when the output voltage regulates, or after 2ms, whichever comes first. In shutdown, the output disconnects from the input.
Undervoltage Lockout
The MAX1595 has an undervoltage-lockout that deactivates the devices when the input voltage falls below 1.6V. Below UVLO, hysteresis holds the device in shutdown until the input voltage rises 40mV above the lockout threshold.
Applications Information
Using white LEDs to backlight LCDs is an increasingly popular approach for portable information devices (Figure 2). Because the forward voltage of white LEDs
4
_______________________________________________________________________________________
Regulated 3.3V/5.0V Step-Up/Step-Down Charge Pump MAX1595
exceeds the available battery voltage, the use of a charge pump such as the MAX1595 provides high efficiency, small size, and constant light output with changing battery voltages. If the output is used only to light LEDs, the output capacitor can be greatly reduced. The frequency modulation of the LED intensity is not discernible to the human eye, and the smaller capacitor saves both size and cost. Adding two Schottky diodes and two capacitors implements a tripler and allows the MAX1595_ _ _50 to regulate a current of 75mA with a supply voltage as low as 2.3V (Figure 3).
CX = 0.1F
CXP
CXN
MAX1595_ _ _50
VIN IN OUT AOUT CIN = 1F SHDN PGND GND COUT = 0.47F 100 100 100
Capacitor Selection
The MAX1595 requires only three external capacitors (Figure 4). Their values are closely linked to the output current capacity, oscillator frequency, output noise content, and mode of operation. Generally, the transfer capacitor (CX) will be the smallest, and the input capacitor (CIN) is twice as large as CX. Higher switching frequencies allow the use of the smaller CX and CIN. The output capacitor (COUT) can be anywhere from 5-times to 50-times larger than CX. Table 1 shows recommended capacitor values. In addition, the following equation approximates output ripple: VRIPPLE IOUT / (2 x fOSC x COUT) Table 2 lists the manufacturers of recommended capacitors. Ceramic capacitors will provide the lowest ripple due to their typically lower ESR.
Figure 2. White LED Bias Supply
INPUT 2.3V
IN SHDN
AOUT OUT 1F 0.22F OUTPUT REGULATED 5V 1F 75mA
1F
MAX1595_ _ _50
CXP 0.22F PGND GND CXN
Power Dissipation
The power dissipated in the MAX1595 depends on output current and is accurately described by: PDISS = IOUT (2VIN - VOUT) PDISS must be less than that allowed by the package rating.
Figure 3. Regulated Voltage Tripler
Layout Considerations
All capacitors should be soldered in close proximity to the IC. Connect ground and power ground through a short, low-impedance trace. The input supply trace should be as short as possible. Otherwise, an additional input supply filter capacitor (tantalum or electrolytic) may be required.
ON OFF IN CIN 1F 3 2 SHDN
CXP CXN IN PGND 5
7 6 8 1 COUT 1F CX 0.22F OUT
MAX1595
OUT GND 4 AOUT
Figure 4. Standard Operating Circuit _______________________________________________________________________________________ 5
Regulated 3.3V/5.0V Step-Up/Step-Down Charge Pump MAX1595
Table 1. Recommended Capacitor Values
OUTPUT RIPPLE (mV) 70 35 CIN (F) 1 2.2 CX (F) 0.22 0.47 COUT (F) 1 2.2
Table 2. Recommended Capacitor Manufacturers
VALUE (F) 1 0.22 0.47 0.1 VOLTAGE (V) 10 10 10 10 TYPE X7R X7R X7R X7R SIZE 0805 0603 0603 0603 MANUFACTURER Taiyo Yuden Taiyo Yuden Taiyo Yuden Taiyo Yuden PART LMK212BJ105MG LMK107BJ224MA LMK107BJ474MA LMK107BJ104MA
Pin Configurations (continued)
TOP VIEW
AOUT 12 SHDN IN IN 1 2 3 OUT 11 OUT 10 9 8 7 CXP CXN CXN
Chip Information
TRANSISTOR COUNT: 1370
MAX1595
4 GND
5 PGND
6 PGND
THIN QFN 4mm x 4mm
6
_______________________________________________________________________________________
Regulated 3.3V/5.0V Step-Up/Step-Down Charge Pump
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
8LUMAXD.EPS
MAX1595
8
4X S
8
INCHES DIM A A1 A2 b c D e E H MIN 0.002 0.030 MAX 0.043 0.006 0.037
MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95
y 0.500.1 0.60.1
E
H
1
0.60.1
1
D
L
S
BOTTOM VIEW
0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6 0 0.0207 BSC
0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC
TOP VIEW
A2
A1
A
e
c b L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0036
J
1 1
_______________________________________________________________________________________
7
Regulated 3.3V/5.0V Step-Up/Step-Down Charge Pump MAX1595
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE 12,16,20,24L QFN THIN, 4x4x0.8 mm
21-0139
A
PACKAGE OUTLINE 12,16,20,24L QFN THIN, 4x4x0.8 mm
21-0139
A
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) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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