19-2107; Rev 3; 10/11
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 1µF for 125mA of output current. The com-
plete regulator requires three external capacitors—no
inductor is needed. The MAX1595 is specifically
designed to serve as a high-power, high- efficiency aux-
iliary supply in applications that demand a compact
design. The MAX1595 is offered in space-saving 8-pin
µMAX
®
and high-power 12-pin TQFN 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
220µA Quiescent Current
o
0.1µA 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
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Ordering Information
PART
MAX1595EUA33+
MAX1595ETC33+
MAX1595EUA50+
MAX1595ETC50+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 µMAX
12 TQFN-EP*
8 µMAX
12 TQFN-EP*
-40°C to +85°C
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
Selector Guide
PART
MAX1595EUA33+
MAX1595ETC33+
V
OUT
(V)**
3.3
3.3
5.0
TOP MARK
—
AAEH
—
Typical Operating Circuit
MAX1595EUA50+
MAX1595ETC50+
AAEI
5.0
**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
µMAX
Pin Configurations continued at end of data sheet.
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
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 (T
A
= +70°C)
µMAX (derate 4.8mW/°C above +70°C) ..................387.8mW
TQFN-EP (derate 24.4mW/°C above +70°C) .........1951.2mW
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
Soldering Temperature (reflow) .......................................+260°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.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
TQFN
Junction-to-Ambient Thermal Resistance (θ
JA
)..........41°C/W
Junction-to-Case Thermal Resistance (θ
JC
).................6°C/W
Note 1:
µMAX
Junction-to-Ambient Thermal Resistance (θ
JA
).....206.3°C/W
Junction-to-Case Thermal Resistance (θ
JC
)...............42°C/W
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to
www.maxim-ic.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(V
IN
= 2V for MAX1595_ _ _33, V
IN
= 3V for MAX1595_ _ _50, C
IN
= 1µF, C
X
= 0.22µF, C
OUT
= 1µF, T
A
= -40° to +85°C, unless otherwise
noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
Input Voltage Range
Input Undervoltage Lockout
Threshold
Input Undervoltage Lockout
Hysteresis
0 < I
LOAD
< 125mA,
V
IN
= +3.0V
Output Voltage
V
OUT
T
A
= 0°C to +85°C
T
A
= -40°C to +85°C
4.85
4.80
3.20
3.16
3.20
3.16
220
240
0.85
1.0
3.33
3.33
SYMBOL
V
IN
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
µA
MHz
µA
V
V
µA
V
TYP
MAX
5.5
1.72
UNITS
V
V
mV
0 < I
LOAD
< 75mA, V
IN
T
A
= 0°C to +85°C
= +2.0V
T
A
= -40°C to +85°C
0 < I
LOAD
< 30mA, V
IN
T
A
= 0°C to +85°C
= +1.8V
T
A
= -40°C to +85°C
No-Load Input Current
Switching Frequency
Shutdown Supply Current
SHDN
Input Voltage Low
SHDN
Input Voltage High
SHDN
Input Leakage Current
I
Q
f
OSC
I
SHDN
V
INL
V
INH
V
IN
= +2.0V, MAX1595_ _ _33
V
IN
= +3.0V, MAX1595_ _ _50
I
LOAD
> 20mA, V
OUT
> V
IN
V
SHDN
= 0V, V
IN
= +5.5V, V
OUT
= 0V
V
IN
= 2.0V to 5.5V
V
IN
= 2.0V to 5.5V
Note 2:
Specifications to -40°C 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, V
IN
= 2V for MAX1595_ _ _33, V
IN
= 3V for MAX1595_ _ _50, T
A
= +25°C, 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
V
IN
= 3V
V
IN
= 3.3V
V
IN
= 3.6V
MAX1595 toc03
10000
5.06
1000
SUPPLY CURRENT (µA)
10
1
V
OUT
= 5V
0
1
2
3
4
5
6
V
OUT
= 5V
50mV/div
100
0.1
SUPPLY VOLTAGE (V)
4.90
200ns/div
OUTPUT WAVEFORM. AC-COUPLED.
V
IN
= 3.6V, I
LOAD
= 100mA, C
OUT
= 1µF
1
10
100
LOAD CURRENT (mA)
V
OUT
= 5V
1000
3V EFFICIENCY
vs. LOAD CURRENT
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
1
10
LOAD CURRENT (mA)
100
V
IN
= 2.4V
V
IN
= 1.8V
MAX1595 toc04
5V EFFICIENCY
vs. LOAD CURRENT
90
80
EFFICEINCY (%)
MAX1595 toc05
SHUTDOWN TIMING
MAX1595 toc06
100
100
V
IN
= 3V
5V
A
70
60
50
40
30
20
10
0
0.1
1
10
100
1000
LOAD CURRENT (mA)
100µs/div
A: OUTPUT VOLTAGE: R
L
= 100Ω, 2V/div
B: SHDN VOLTAGE: 2V/div
V
IN
= 3.6V
B
V
IN
= 3.3V
LINE-TRANSIENT RESPONSE
MAX1595 toc07
LOAD-TRANSIENT RESPONSE
MAX1595 toc08
OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
V
OUT
= 5V, I
LOAD
= 125mA
MAX1595 toc09
6
A
A
OUTPUT VOLTAGE (V)
4
3
2
1
C
OUT
= 1µF
0
2ms/div
A: INPUT VOLTAGE: V
IN
= 3.1V TO 3.6V, 500mV/div
B: OUTPUT VOLTAGE: I
LOAD
= 50mA, 100mV/div
200µs/div
A: LOAD CURRENT: I
LOAD
= 5mA to 95mA, 100mA/div
B: OUTPUT VOLTAGE: AC-COUPLED 100mV/div
0
1
2
3
4
5
6
SUPPLY VOLTAGE (V)
V
OUT
= 3.3V, I
LOAD
= 75mA
5
B
B
_______________________________________________________________________________________
3
Regulated 3.3V/5.0V Step-Up/
Step-Down Charge Pump
MAX1595
Pin Description
PIN
µMAX
1
2
3
4
5
6
7
8
—
TQFN-EP
12
1
2, 3
4
5, 6
7, 8
9
10, 11
—
NAME
AOUT
SHDN
IN
GND
PGND
CXN
CXP
OUT
EP
FUNCTION
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 1μF 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.
Exposed Pad. Internally connected to GND. Connect to a large ground plane to
maximize thermal performance. Not intended as an electrical connection point (TQFN
package only).
Detailed Description
The MAX1595 charge pump provides either a 3.3V or 5V
regulated output. It delivers a maximum 125mA load cur-
rent. 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 com-
plete regulator circuit requires only three small external
capacitors. An innovative control scheme provides con-
stant 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 (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 C
X
, 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
(C
X
) to the output capacitor (C
OUT
).
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 unregulat-
ed charge-pump voltage doubler. The oscillator runs at a
50% duty cycle. During one half of the period, the trans-
fer capacitor (C
X)
charges to the input voltage. During
the other half, the doubler transfers the sum of C
X
and
input voltage to the output filter capacitor (C
OUT
). Rather
4
IN
S1
C
X
S2
OUT
C
IN
C
OUT
OSC
Figure 1. Unregulated Voltage Doubler
than doubling the input voltage, the MAX1595 provides a
regulated output voltage of either 3.3V or 5.0V.
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 volt-
age regulates, or after 2ms, whichever comes first. In
shutdown, the output disconnects from the input.
Undervoltage Lockout
The MAX1595 has an undervoltage-lockout that deacti-
vates 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.
_______________________________________________________________________________________
Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
MAX1595
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
exceeds the available battery voltage, the use of a
charge pump such as the MAX1595 provides high effi-
ciency, small size, and constant light output with chang-
ing 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 dis-
cernible to the human eye, and the smaller capacitor
saves both size and cost.
Adding two Schottky diodes and two capacitors imple-
ments a tripler and allows the MAX1595_ _ _50 to regu-
late a current of 75mA with a supply voltage as low as
2.3V (Figure 3).
C
X
= 0.1µF
CXP
CXN
MAX1595_ _ _50
V
IN
IN
OUT
AOUT
C
IN
= 1µF
SHDN
PGND GND
C
OUT
=
0.47µF
100Ω
100Ω
100Ω
Figure 2. White LED Bias Supply
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 con-
tent, and mode of operation.
Generally, the transfer capacitor (C
X
) will be the smallest,
and the input capacitor (C
IN
) is twice as large as C
X
.
Higher switching frequencies allow the use of the smaller
C
X
and C
IN
. The output capacitor (C
OUT
) can be any-
where from 5-times to 50-times larger than C
X
. Table 1
shows recommended capacitor values.
In addition, the following equation approximates output
ripple:
V
RIPPLE
≅
I
OUT
/ (2 x f
OSC
x C
OUT
)
Table 2 lists the manufacturers of recommended capaci-
tors. Ceramic capacitors will provide the lowest ripple
due to their typically lower ESR.
Figure 3. Regulated Voltage Tripler
INPUT
2.3V
IN
SHDN
1µF
AOUT
OUT
1µF
0.22µF
OUTPUT
REGULATED 5V
1µF 75mA
MAX1595_ _ _50
CXP
0.22µF
PGND GND
CXN
Power Dissipation
The power dissipated in the MAX1595 depends on out-
put current and is accurately described by:
P
DISS
= I
OUT
(2V
IN
- V
OUT
)
ON
CXP
2
3
OFF
IN
C
IN
1µF
SHDN
CXN
IN
PGND
5
7
6
8
1
C
OUT
1µF
C
X
0.22µF
OUT
P
DISS
must be less than that allowed by the package
rating.
MAX1595
OUT
GND
4
AOUT
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.
Figure 4. Standard Operating Circuit
5
_______________________________________________________________________________________
综合技术交流
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
