19-0211; Rev 4; 5/96
KIT
ATION
EVALU
E
BL
AVAILA
3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters
____________________________Features
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
0.8V to 6.0V Input Supply Voltage
0.8V Typ Start-Up Supply Voltage
85% Efficiency at 100mA
25µA Quiescent Current
1µA Shutdown Mode
125mA and 500mA Switch-Current Limits Permit
Use of Low-Cost Inductors
Up to 500kHz Switching Frequency
±1.5% Reference Tolerance Over Temperature
Low-Battery Detector (LBI/LBO)
8-Pin SO and µMAX Packages
_______________General Description
The MAX856–MAX859 are high-efficiency, CMOS, step-
up, DC-DC switching regulators for small, low input volt-
age or battery-powered systems. The MAX856/MAX858
accept a positive input voltage between 0.8V and V
OUT
and convert it to a higher, pin-selectable output voltage of
3.3V or 5V. The MAX857/MAX859 adjustable versions
accept 0.8V to 6.0V input voltages and generate higher
adjustable output voltages in the 2.7V to 6.0V range.
Typical efficiencies are greater than 85%. Typical quies-
cent supply current is 25µA (1µA in shutdown).
The MAX856–MAX859 combine ultra-low quiescent supply
current and high efficiency to give maximum battery life. An
internal MOSFET power transistor permits high switching
frequencies. This benefit, combined with internally set peak
inductor current limits, permits the use of small, low-cost
inductors. The MAX856/MAX857 have a 500mA peak
inductor current limit. The MAX858/MAX859 have a 125mA
peak inductor current limit.
MAX856–MAX859
______________Ordering Information
PART
MAX856CSA
MAX856CUA
MAX856C/D
MAX856ESA
MAX856MJA
MAX857CSA
MAX857CUA
MAX857C/D
MAX857ESA
MAX857MJA
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
8 SO
8 µMAX
Dice*
8 SO
8 CERDIP
†
8 SO
8 µMAX
Dice*
8 SO
8 CERDIP
†
________________________Applications
3.3V to 5V Step-Up Conversion
Palmtop Computers
Portable Data-Collection Equipment
Personal Data Communicators/Computers
Medical Instrumentation
2-Cell & 3-Cell Battery-Operated Equipment
Glucose Meters
__________Typical Operating Circuit
INPUT
0.8V TO V
OUT
Ordering Information continued at end of data sheet.
* Dice are tested at T
A
= +25°C only.
†
Contact factory for availability.
__________________Pin Configuration
TOP VIEW
47µH
OUTPUT
5V AT 100mA
OR
3.3V AT 125mA
68µF
SHDN
3/5
1
2
8
7
LX
GND
OUT
LBI
ON/OFF
SHDN
LX
1N5817
REF
3
LBO
4
MAX856
MAX858
6
5
MAX856
3V/5V SELECT
LOW-BATTERY
DETECTOR
INPUT
3/5
LBI
REF
LBO
LOW-BATTERY
DETECTOR OUTPUT
OUT
SHDN
FB
1
2
SO/µMAX
8
7
LX
GND
OUT
LBI
GND
REF
3
LBO
4
MAX857
MAX859
6
5
SO/µMAX
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters
MAX856–MAX859
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (OUT to GND) ...................................-0.3V, +7V
Switch Voltage (LX to GND) .......................................-0.3V, +7V
— —
— –
SHDN , LBO to GND ....................................................-0.3V, +7V
–
–
LBI, REF, 3/ 5, FB to GND .........................-0.3V, (V
OUT
+ 0.3V)
Reference Current (I
REF
) ..................................................2.5mA
Continuous Power Dissipation (T
A
= +70°C)
SO (derate 5.88mW/°C above +70°C) .........................471mW
µMAX (derate 4.1mW/°C above +70°C) ......................330mW
CERDIP (derate 8.00mW/°C above +70°C) .................640mW
Reverse Battery Current (T
A
≤
+45°C, Note 1) .................750mA
Operating Temperature Ranges
MAX85_C_ _ ......................................................0°C to +70°C
MAX85_E_ _ ....................................................-40°C to +85°C
MAX85_MJA .................................................-55°C to +125°C
Junction Temperature .....................................................+150°C
Storage Temperature Range ............................-65°C to +160°C
Lead Temperature (soldering, 10sec) ............................+300°C
Note 1:
Reverse battery current is measured from the
Typical Operating Circuit’s
battery input terminal to GND when the battery is
connected backwards. A reverse current of 750mA will not exceed the SO or CERDIP package dissipation limits but, if left
for an extended time (more than ten minutes), may degrade performance.
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
(Circuits of Figure 2, V
IN
= 2.5V, I
LOAD
= 0mA, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
CONDITIONS
–
–
MAX856, 3/ 5 = 0V, 0mA
≤
I
LOAD
≤
100mA
–
–
MAX856, 3/ 5 = 3V, 0mA
≤
I
LOAD
≤
150mA
2V
≤
V
IN
≤
3V
MAX857, V
OUT
= 5V, 0mA
≤
I
LOAD
≤100mA
–
–
MAX858, 3/ 5 = 0V, 0mA
≤
I
LOAD
≤
25mA
–
–
MAX858, 3/ 5 = 3V, 0mA
≤
I
LOAD
≤
35mA
MAX859, V
OUT
= 5V, 0mA
≤
I
LOAD
≤
25mA
Minimum Start-Up
Supply Voltage
Minimum Operating Voltage
Quiescent Supply Current in
3.3V Mode (Note 2)
No Load Battery Current
Shutdown Quiescent Current
(Note 2)
Peak Inductor Current Limit
Reference Voltage
–
–
I
LOAD
= 0mA, 3/ 5 = 3V, LBI = 1.5V, V
OUT
= 3.47V,
(FB = 1.5V, MAX857/MAX859 only)
Output set for 3.3V, measured at V
IN
in Figure 2, R3 omitted.
— —
— –
–
–
SHDN = 0V, 3/ 5 = 3V, LBI = 1.5V, V
OUT
= 3.47V,
(FB = 1.5V, MAX857/MAX859 only)
MAX856/MAX857
MAX858/MAX859
1.23
MAX85_C
MAX85_E/M
1
500
125
1.25
0.8
1.22
1.25
25
I
SINK
= 2mA
LBO = 5V
0.4
1
1.27
2.0
1.28
I
LOAD
= 0mA
MIN
4.80
3.17
4.80
4.80
3.17
4.80
TYP
5.0
3.3
5.0
5.0
3.3
5.0
0.8
0.8
25
60
MAX UNITS
5.20
3.43
5.20
5.20
3.43
5.20
1.8
V
V
µA
V
Output Voltage
60
1
5
µA
µA
mA
V
%
V
mV
V
µA
No REF load
–
–
Reference-Voltage Regulation 3/ 5 = 3V, -20µA
≤
REF load
≤
250µA, C
REF
= 0.22µF
LBI Input Threshold
LBI Input Hysteresis
LBO Output Voltage Low
LBO Output Leakage Current
With falling edge
2
_______________________________________________________________________________________
3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters
ELECTRICAL CHARACTERISTICS (continued)
(Circuits of Figure 2, V
IN
= 2.5V, I
LOAD
= 0mA, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
–— – –
— —
–
SHDN , 3/ 5 Input Voltage Low
— —
— – –
–
SHDN , 3/ 5 Input Voltage High
— —
— – –
–
SHDN , 3/ 5, FB, LBI Input Current
FB Voltage
Output Voltage Range
0.4
1.6
–— –
— —
–
–
LBI = 1.5V, FB = 1.5V, SHDN = 0V or 3V, 3/ 5 = 0V or 3V
MAX857/MAX859
MAX857/MAX859, I
LOAD
= 0mA (Note 3)
1.22
2.7
1.25
±100
1.28
6.0
V
V
nA
V
V
MAX856–MAX859
Note 2:
Supply current from the 3.3V output is measured with an ammeter between the 3.3V output and OUT pin. This current
correlates directly with actual battery supply current, but is reduced in value according to the step-up ratio and efficiency.
V
OUT
= 3.47V to keep the internal switch open when measuring the current into the device.
Note 3:
Minimum value is production tested. Maximum value is guaranteed by design and is not production tested.
__________________________________________Typical Operating Characteristics
(Circuits of Figure 2, T
A
= +25°C, unless otherwise noted.)
MAX858/MAX859
EFFICIENCY vs. OUTPUT CURRENT
V
OUT
= 3.3V
MAX856-01
MAX858/MAX859
EFFICIENCY vs. OUTPUT CURRENT
V
OUT
= 5V
90
80
V
IN
= 3.3V
MAX856-02
100
90
80
EFFICIENCY (%)
V
IN
= 2.0V
V
IN
= 1.5V
V
IN
= 2.5V
100
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.001
0.01
70
60
50
40
30
20
10
0
V
IN
= 1.5V
V
IN
= 2.5V
1
0.1
100
10
LOAD CURRENT (mA)
1000
0.001
0.01
1
0.1
100
10
LOAD CURRENT (mA)
1000
MAX856/MAX857
EFFICIENCY vs. OUTPUT CURRENT
V
OUT
= 5V
90
80
EFFICIENCY (%)
V
IN
= 2.0V
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.001 0.01
100
1
0.1
10
LOAD CURRENT (mA)
1000
V
IN
= 1.5V
V
IN
= 3.3V
MAX856-03
MAX856/MAX857
EFFICIENCY vs. OUTPUT CURRENT
V
OUT
= 3.3V
90
80
70
60
50
40
30
20
10
0
0.001 0.01
100
1
0.1
10
LOAD CURRENT (mA)
1000
V
IN
= 1.5V
V
IN
= 2.0V
V
IN
= 2.5V
MAX856-04
100
100
_______________________________________________________________________________________
3
3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters
MAX856–MAX859
_____________________________Typical Operating Characteristics (continued)
(Circuits of Figure 2, T
A
= +25°C, unless otherwise noted.)
MAX856/MAX857
NO LOAD BATTERY CURRENT
vs. INPUT VOLTAGE
MAX856-08
MAX856-05
REFERENCE VOLTAGE vs. CURRENT
10
9
V
REF
LOAD REGULATION (mV)
8
7
6
5
4
3
2
1
0
0
100
200
50
150
REFERENCE LOAD CURRENT (µA)
250
400
350
QUIESCENT CURRENT (µA)
300
250
200
150
100
50
0
1.5
MAX858/MAX859
NO LOAD BATTERY CURRENT
vs. INPUT VOLTAGE
1.4
QUIESCENT CURRENT (mA)
1.2
1.0
0.8
0.6
0.4
0.2
0
T
A
= -40°C
1.5
2.0
2.5
3.0
3.5
4.0
T
A
= +25°C
T
A
= +85°C
INCLUDES ALL EXTERNAL
COMPONENT LEAKAGES.
CAPACITOR LEAKAGE
DOMINATES AT T
A
= +85°C.
CAPS ARE SPRAGUE 595D
MAX856-09
1.6
T
A
= +85°C
INCLUDES ALL EXTERNAL
COMPONENT LEAKAGES.
CAPACITOR LEAKAGE
DOMINATES AT T
A
= +85°C.
CAPS ARE SPRAGUE 595 D
T
A
= +25°C
T
A
= -40°C
2.0
2.5
3.0
3.5
4.0
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
QUIESCENT CURRENT
vs. INPUT VOLTAGE
MAX856-10
MAX856/MAX857
MINIMUM START-UP INPUT VOLTAGE
vs. LOAD CURRENT
MAX856-06
START-UP INPUT VOLTAGE (V)
START-UP INPUT VOLTAGE (V)
1.4
QUIESCENT CURRENT (mA)
1.2
1.0
0.8
0.6
0.4
0.2
0
T
A
= -40°C
1.5
2.0
2.5
SEE NOTE 2
IN THE ELECTRICAL
CHARACTERISTICS
V
OUT
= 5V
1.10
1.05
1.00
0.95
0.90
0.85
0.80
0.75
V
OUT
= 3.3V
1.3
1.2
V
OUT
= 5V
1.1
1.0
0.9
0.8
T
A
= +85°C
3.0
3.5
4.0
0.1
1
10
100
0.1
1
10
100
INPUT VOLTAGE (V)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
SHUTDOWN CURRENT
vs. INPUT VOLTAGE
MAX856-11
MAX856/MAX857
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX856-13
MAX858/MAX859
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
90
80
LOAD CURRENT (mA)
MAX856-12
1.0
0.9
SHUTDOWN CURRENT (µA)
0.8
400
350
LOAD CURRENT (mA)
300
250
V
OUT
= 3.3V
200
150
100
V
OUT
= 5.0V
100
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1.5
2.0
2.5
3.0
3.5
4.0
INPUT VOLTAGE (V)
T
A
= -40°C
T
A
= +85°C
T
A
= +25°C
70
60
50
40
30
20
10
0
V
OUT
= 3.3V
V
OUT
= 5.0V
50
0
1.0
1.5
2.0
2.5
3.0
3.5
4.0
INPUT VOLTAGE (V)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
INPUT VOLTAGE (V)
4
_______________________________________________________________________________________
MAX856-07
1.6
1.15
MAX858/MAX859
MINIMUM START-UP INPUT VOLTAGE
vs. LOAD CURRENT
1.4
3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters
MAX856–MAX859
_____________________________Typical Operating Characteristics (continued)
(Circuits of Figure 2, T
A
= +25°C, unless otherwise noted.)
MAX856/MAX857
LINE-TRANSIENT RESPONSE (5V MODE)
MAX856/MAX857
LOAD-TRANSIENT RESPONSE (5V MODE)
V
OUT
50mV/div
V
OUT
50mV/div
3V
V
IN
2V
I
LOAD
0mA to 100mA
2ms/div
V
IN
= 2.5V
50µs/div
MAX859 LINE-TRANSIENT RESPONSE
MAX858/MAX859 LOAD-TRANSIENT RESPONSE
V
OUT
50mV/div
V
OUT
50mV/div
3V
V
IN
2V
1V/div
I
LOAD
0mA to 25mA
0
25
1ms/div
V
IN
= 2.5V
2ms/div
MAX856 START-UP DELAY (5V MODE)
MAX858/MAX859 START-UP DELAY (5V MODE)
V
OUT
2V/div
V
OUT
2V/div
V
SHDN
5V/div
V
SHDN
5V/div
V
IN
= 2.5V, I
LOAD
= 100mA
5ms/div
V
IN
= 2.5V, I
LOAD
= 25mA
5ms/div
_______________________________________________________________________________________
5
单片机
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
