MAXIM MAX1595EGC33

19-2107; Rev 0; 7/01
Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
Features
♦ Ultra-Small: Requires Only Three Ceramic
Capacitors
♦ No Inductors Required
♦ Up to 125mA Output Current
♦ Regulated ±3% Output Voltage
♦ 1MHz Switching Frequency
♦ 1.8V to 5.5V Input Voltage
♦ 220µA Quiescent Current
♦ 0.1µA Shutdown Current
♦ Load Disconnect in Shutdown
Applications
Ordering Information
White LED Power
PART
Flash Memory Supplies
TEMP. RANGE
PINPACKAGE
8 µMAX
Battery-Powered Applications
MAX1595EUA33
-40°C to +85°C
Miniature Equipment
MAX1595EGC33
-40°C to +85°C
12 QFN
PCMCIA Cards
MAX1595EUA50
-40°C to +85°C
8 µMAX
3.3V to 5V Local Conversion Applications
MAX1595EGC50
-40°C to +85°C
12 QFN
Selector Guide
Backup-Battery Boost Converters
3V to 5V GSM SIMM Cards
VOUT *
TOP
MARK
MAX1595EUA33
MAX1595EGC33
3.3V
—
3.3V
AAAP
MAX1595EUA50
5.0V
—
5.0V
AAAM
PART
Typical Operating Circuit
MAX1595EGC50
*Contact factory for other fixed-output voltages from 2.7V to 5.0V.
Pin Configurations
CXN
INPUT
CXP
TOP VIEW
MAX1595
IN
OUT
AOUT
SHDN
PGND GND
OUTPUT
AOUT
1
8
SHDN
2
7
CXP
IN
3
6
CXN
GND
4
5
PGND
MAX1595
OUT
µMAX
Pin Configurations continued at end of data sheet.
Maxim Integrated Products
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.
1
MAX1595
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 1µF 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 µMAX and high-power 12-pin QFN packages.
MAX1595
Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
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 6.0V)
Continuous Output Current ...............................................150mA
Continuous Power Dissipation (TA = +70°C)
8-Pin µMAX (derate 4.5mW/°C above +70°C) ............362mW
12-Pin QFN (derate 18.5mW/°C above +70°C) ........1481mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (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
(VIN = +2V for MAX1595_ _ _33, VIN = +3V for MAX1595_ _ _50, CIN = 1µF, CX = 0.22µF, COUT = 1µF, TA = -40° to +85°C, unless
otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
Input Voltage Range
SYMBOL
CONDITIONS
VIN
MIN
Input Undervoltage Lockout
Threshold
1.40
Input Undervoltage Lockout
Hysteresis
No-Load Input Current
Switching Frequency
1.60
TA = 0 to +85°C
4.85
TA = -40°C to +85°C
4.80
0 < ILOAD < 75mA, VIN TA = 0 to +85°C
= +2.0V
TA = -40°C to +85°C
3.20
VOUT
0 < ILOAD < 30mA, VIN TA = 0 to +85°C
= +1.8V
TA = -40°C to +85°C
3.20
IQ
UNITS
5.5
V
1.72
V
fOSC
5.05
mV
5.15
5.20
3.33
3.16
3.40
3.44
3.33
3.16
V
3.40
3.44
VIN = +2.0V, MAX1595_ _ _33
220
320
VIN = +3.0V, MAX1595_ _ _50
240
350
1.0
1.15
MHz
ILOAD > 20mA, VOUT > VIN
0.85
SHDN = 0, VIN = +5.5V, VOUT = 0
Shutdown Supply Current
I SHDN
SHDN Input Voltage Low
VINL
VIN = 2.0V to 5.5V
SHDN Input Voltage High
VINH
VIN = 2.0V to 5.5V
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
_______________________________________________________________________________________
µA
5
µA
0.6
V
0.1
µA
1.6
SHDN Input Leakage Current
2
MAX
40
0 < ILOAD < 125mA,
VIN = +3.0V
Output Voltage
TYP
1.8
V
Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
MAX1595 toc02
5.06
MAX1595 toc01
10000
5.04
50mV/div
100
10
OUTPUT VOLTAGE (V)
1000
SUPPLY CURRENT (µA)
OUTPUT VOLTAGE
vs. LOAD CURRENT
OUTPUT WAVEFORM
MAX1595 toc03
NO LOAD SUPPLY CURRENT
vs. SUPPLY VOLTAGE
VIN = 3.6V
5.02
VIN = 3.3V
5.00
4.98
VIN = 3.0V
4.96
4.94
1
4.92
VOUT = 5.0V
VOUT = 5V
0.1
1
2
3
4
5
6
200ns/div
OUTPUT WAVEFORM. AC-COUPLED.
VIN = 3.6V, ILOAD = 100mA, COUT = 1µF
SUPPLY VOLTAGE (V)
VIN = 1.8V
80
VIN = 2.4V
50
40
MAX1595 toc06
VIN = 3.0V
80
EFFICEINCY (%)
70
90
1000
100
SHUTDOWN TIMING
100
MAX1595 toc04
100
60
10
LOAD CURRENT (mA)
5V EFFICIENCY
vs. LOAD CURRENT
3V EFFICIENCY
vs. LOAD CURRENT
90
1
MAX1595 toc05
0
5V
A
70
VIN = 3.3V
60
VIN = 3.6V
50
40
30
30
20
20
10
10
B
0
0
1
10
0.1
100
1
10
100
100µs/div
A: OUTPUT VOLTAGE: RL = 100Ω, 2V/div
B: SHDN VOLTAGE: 2V/div
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LINE-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
MAX1595 toc08
MAX1595 toc07
A
MAX1595 toc09
6
VOUT = 5.0V, ILOAD = 125mA
5
A
B
B
OUTPUT VOLTAGE (V)
EFFICIENCY (%)
VOUT = 5V
4.90
4
VOUT = 3.3V, ILOAD = 75mA
3
2
1
COUT = 1µF
0
2ms/div
A: INPUT VOLTAGE: VIN = 3.1V TO 3.6V, 500mV/div
B: OUTPUT VOLTAGE: ILOAD = 50mA, 100mV/div
200µs/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)
_______________________________________________________________________________________
3
MAX1595
__________________________________________Typical Operating Characteristics
(Circuit of Figure 4, VIN = +2.0V for MAX1595_ _ _33, VIN = +3V for MAX1595_ _ _50, TA = +25°C, unless otherwise noted.)
MAX1595
Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
Pin Description
PIN
MAX1595
µMAX
MAX1595
QFN
NAME
FUNCTION
1
12
AOUT
Analog Power and Sense Input for Error Amplifier/Comparator. Connect to OUT at
output filter capacitor.
2
1
SHDN
Shutdown Input. When SHDN = low, the device turns off; when SHDN = high, the device
activates. In shutdown, OUT is disconnected from IN.
3
2, 3
IN
Input Supply. Can range from 1.8V to 5.5V. Bypass to GND with a 1µF capacitor.
4
4
GND
5
5, 6
PGND
Ground
6
7, 8
CXN
Negative Terminal of the Charge-Pump Transfer Capacitor
Power Ground
7
9
CXP
Positive Terminal of the Charge-Pump Transfer Capacitor
8
10, 11
OUT
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.
4
S2
IN
S1
OUT
CX
CIN
COUT
OSC
Figure 1. Unregulated Voltage Doubler
Shutdown
Driving SHDN low places the device in shutdown mode.
The device draws 0.1µA 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
_______________________________________________________________________________________
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 = 0.1µF
CXP
CXN
MAX1595_ _ _50
VIN
IN
OUT
AOUT
SHDN
CIN = 1µF
COUT =
0.47µF
100Ω
100Ω
100Ω
PGND GND
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:
Figure 2. White LED Bias Supply
INPUT
2.3V
IN
AOUT
SHDN
OUTPUT
REGULATED 5V
1µF 75mA
OUT
1µF
1µF
0.22µF
MAX1595_ _ _50
VRIPPLE ≅ IOUT / (2 x fOSC x COUT)
CXP
0.22µF
Table 2 lists the manufacturers of recommended capacitors. Ceramic capacitors will provide the lowest ripple
due to their typically lower ESR.
CXN
PGND GND
Power Dissipation
The power dissipated in the MAX1595 depends on output current and is accurately described by:
Figure 3. Regulated Voltage Tripler
PDISS = IOUT (2VIN - VOUT)
PDISS must be less than that allowed by the package
rating.
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.
CXP
ON
2
OFF
3
IN
CIN
1µF
SHDN
CXN
MAX1595
IN
OUT
PGND
5
GND
4
AOUT
7
6
8
CX
0.22µF
OUT
1
COUT
1µF
Figure 4. Standard Operating Circuit
_______________________________________________________________________________________
5
MAX1595
Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
Table 1. Recommended Capacitor Values
OUTPUT RIPPLE (mV)
CIN (µF)
CX (µF)
COUT (µF)
70
1
0.22
1
35
2.2
0.47
2.2
Table 2. Recommended Capacitor Manufacturers
VALUE (µF)
VOLTAGE (V)
TYPE
SIZE
MANUFACTURER
PART
1
10
X7R
0805
Taiyo Yuden
LMK212BJ105MG
0.22
10
X7R
0603
Taiyo Yuden
LMK107BJ224MA
0.47
10
X7R
0603
Taiyo Yuden
LMK107BJ474MA
0.1
10
X7R
0603
Taiyo Yuden
LMK107BJ104MA
Pin Configurations (continued)
TOP VIEW
SHDN
1
IN
2
IN
3
AOUT
OUT
OUT
12
11
10
MAX1595
4
5
6
GND
PGND
PGND
Chip Information
TRANSISTOR COUNT: 1370
9
CXP
8
CXN
7
CXN
4mm × 4mm QFN
6
_______________________________________________________________________________________
Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
8LUMAXD.EPS
_______________________________________________________________________________________
7
MAX1595
Package Information
Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
12, 16,20, 24L QFN.EPS
MAX1595
Package Information
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
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.