Rainbow Electronics MAX859 User Manual

19-0211; Rev 4; 5/96

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

_______________General Description

The MAX856–MAX859 are high-efficiency, CMOS, step­up, DC-DC switching regulators for small, low input volt­age 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 quies­cent 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.

________________________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

____________________________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

______________Ordering Information

PART TEMP. RANGE PIN-PACKAGE

MAX856CSA

MAX856CUA 0°C to +70°C 8 µMAX
MAX856C/D 0°C to +70°C Dice*
MAX856ESA -40°C to +85°C 8 SO
MAX856MJA -55°C to +125°C 8 CERDIP
MAX857CSA
MAX857CUA 0°C to +70°C 8 µMAX
MAX857C/D
MAX857ESA -40°C to +85°C 8 SO
MAX857MJA -55°C to +125°C 8 CERDIP

Ordering Information continued at end of data sheet.

* Dice are tested at TA= +25°C only.

†

Contact factory for availability.

0°C to +70°C 8 SO

†

0°C to +70°C 8 SO

0°C to +70°C Dice*

†

MAX856–MAX859

INPUT

0.8V TO V

ON/OFF

3V/5V SELECT

LOW-BATTERY

DETECTOR

INPUT

OUT

OUTPUT

5V AT 100mA

SHDN

47µH

LX

1N5817

OR

3.3V AT 125mA

68µF

MAX856

3/5

LBI

REF

________________________________________________________________

GND

OUT

LBO

LOW-BATTERY
DETECTOR OUTPUT

__________________Pin Configuration

TOP VIEW

SHDN

3/5

REF

LBO

SHDN

REF

LBO

FB

1
2

MAX856

3

MAX858

4

SO/µMAX

1
2

MAX857

3

MAX859

4

SO/µMAX

Maxim Integrated Products

8

LX

7

GND

6

OUT

5

LBI

8

LX

7

GND

6

OUT

5

LBI

1

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone]

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (OUT to GND) ...................................-0.3V, +7V

Switch Voltage (LX to GND) .......................................-0.3V, +7V

S—H—D—N–, LBO to GND....................................................-0.3V, +7V

LBI, REF, 3/–5–, FB to GND .........................-0.3V, (V

Reference Current (I
Continuous Power Dissipation (T

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

Note 1: Reverse battery current is measured from the

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.

) ..................................................2.5mA

REF

= +70°C)

A

+ 0.3V)

OUT

Typical Operating Circuit’s

Reverse Battery Current (T
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

battery input terminal to GND when the battery is

≤ +45°C, Note 1) .................750mA

A

MAX856–MAX859

ELECTRICAL CHARACTERISTICS

(Circuits of Figure 2, VIN= 2.5V, I

= 0mA, TA= T

LOAD

MIN

to T

, unless otherwise noted. Typical values are at TA= +25°C.)

MAX

Output Voltage

Minimum Start-Up
Supply Voltage

Quiescent Supply Current in

3.3V Mode (Note 2)

Shutdown Quiescent Current
(Note 2)

Peak Inductor Current Limit

CONDITIONS

MAX856, 3/–5–= 0V, 0mA ≤ I
MAX856, 3/–5–= 3V, 0mA ≤ I

2V ≤ VIN≤ 3V

I

= 0mA

LOAD

I

= 0mA, 3/–5–= 3V, LBI = 1.5V, V

LOAD

(FB = 1.5V, MAX857/MAX859 only)

Output set for 3.3V, measured at VINin Figure 2, R3 omitted.

S—H—D—N–= 0V, 3/–5–= 3V, LBI = 1.5V, V
(FB = 1.5V, MAX857/MAX859 only)

MAX856/MAX857
MAX858/MAX859
No REF load
3/–5–= 3V, -20µA ≤ REF load ≤ 250µA, C
With falling edge

I

= 2mA

SINK

LBO = 5V

MAX857, V
MAX858, 3/–5–= 0V, 0mA ≤ I
MAX858, 3/–5–= 3V, 0mA ≤ I
MAX859, V

= 5V, 0mA ≤ I

OUT

= 5V, 0mA ≤ I

OUT

OUT

OUT

REF

= 3.47V,

= 3.47V,

LOAD
LOAD
LOAD
LOAD
LOAD
LOAD

= 0.22µF

≤ 100mA
≤ 150mA
≤100mA
≤ 25mA
≤ 35mA
≤ 25mA

MAX85_C
MAX85_E/M

4.80 5.0 5.20

3.17 3.3 3.43

4.80 5.0 5.20

4.80 5.0 5.20

3.17 3.3 3.43

4.80 5.0 5.20

1

15
500
125

UNITSMIN TYP MAXPARAMETER

V

V0.8 1.8
V0.8Minimum Operating Voltage

µA25 60

µA60No Load Battery Current

µA

mA

V1.23 1.25 1.27Reference Voltage

%0.8 2.0Reference-Voltage Regulation

V1.22 1.25 1.28LBI Input Threshold

mV25LBI Input Hysteresis

V0.4LBO Output Voltage Low

µA1LBO Output Leakage Current

2 _______________________________________________________________________________________

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

ELECTRICAL CHARACTERISTICS (continued)

(Circuits of Figure 2, VIN= 2.5V, I

–S—H—D—N–

, 3/–5–Input Voltage Low
S—H—D—N–, 3/–5–Input Voltage High 1.6 V
S—H—D—N–, 3/–5–, FB, LBI Input Current LBI = 1.5V, FB = 1.5V, –S—H—D—N–= 0V or 3V, 3/–5–= 0V or 3V ±100 nA
FB Voltage MAX857/MAX859 1.22 1.25 1.28 V
Output Voltage Range MAX857/MAX859, I

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

= 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.

OUT

= 0mA, TA= T

LOAD

to T

MIN

LOAD

, unless otherwise noted. Typical values are at TA= +25°C.)

MAX

= 0mA (Note 3) 2.7 6.0 V

0.4 V

__________________________________________Typical Operating Characteristics

(Circuits of Figure 2, TA= +25°C, unless otherwise noted.)

MAX858/MAX859

EFFICIENCY vs. OUTPUT CURRENT

V

100

90
80
70
60
50
40

EFFICIENCY (%)

30
20
10

0

0.1

0.010.001
LOAD CURRENT (mA)

OUT

= 3.3V

VIN = 1.5V

1

VIN = 2.5V

VIN = 2.0V

10

100 1000

MAX856-01

100

90
80
70
60
50
40

EFFICIENCY (%)

30
20
10

0

MAX858/MAX859

EFFICIENCY vs. OUTPUT CURRENT

V

= 5V

OUT

VIN = 3.3V

VIN = 2.5V

1

10

100 1000

0.1

0.010.001
LOAD CURRENT (mA)

VIN = 1.5V

MAX856-02

MAX856–MAX859

MAX856/MAX857

EFFICIENCY vs. OUTPUT CURRENT

100

90
80
70
60
50
40

EFFICIENCY (%)

30
20
10

0

0.1

0.010.001
LOAD CURRENT (mA)

V

OUT

= 5V

VIN = 2.0V

1

VIN = 3.3V

10

VIN = 1.5V

100 1000

MAX856-03

100

90
80
70
60
50
40

EFFICIENCY (%)

30
20
10

0

MAX856/MAX857

EFFICIENCY vs. OUTPUT CURRENT

V

= 3.3V

OUT

VIN = 2.5V

VIN = 1.5V

VIN = 2.0V

0.1

0.010.001
LOAD CURRENT (mA)

1

10

100 1000

MAX856-04

_______________________________________________________________________________________

3

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

_____________________________Typical Operating Characteristics (continued)

(Circuits of Figure 2, TA= +25°C, unless otherwise noted.)

REFERENCE VOLTAGE vs. CURRENT



10

9
8
7
6
5
4
3

LOAD REGULATION (mV)

REF

2

V

MAX856–MAX859

1
0

0

50 150 250

REFERENCE LOAD CURRENT (µA)

1.6

1.4

1.2

1.0

0.8

0.6

0.4

QUIESCENT CURRENT (mA)

0.2
TA = -40°C

0

1.5

2.0

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

SHUTDOWN CURRENT (µA)

0.2

TA = -40°C

0.1

0

2.0

1.5

100 200

QUIESCENT CURRENT

vs. INPUT VOLTAGE

SEE NOTE 2
IN THE ELECTRICAL
CHARACTERISTICS

2.5 3.0

INPUT VOLTAGE (V)

SHUTDOWN CURRENT

vs. INPUT VOLTAGE

TA = +85°C

TA = +25°C

2.5 3.0

INPUT VOLTAGE (V)

TA = +85°C

3.5

3.5

4.0

4.0

400
350

MAX856-05

300
250
200

150
100

QUIESCENT CURRENT (µA)

50

0

1.5

1.15

MAX856-10

1.10

1.05

1.00

0.95

0.90

0.85

START-UP INPUT VOLTAGE (V)

0.80

0.75

0.1 10

400

MAX856-11

350
300
250
200
150

LOAD CURRENT (mA)

100

50

0

1.0

MAX856/MAX857

NO LOAD BATTERY CURRENT

vs. INPUT VOLTAGE

TA = +85°C

INCLUDES ALL EXTERNAL
COMPONENT LEAKAGES.
CAPACITOR LEAKAGE
DOMINATES AT T
CAPS ARE SPRAGUE 595 D

TA = +25°C

TA = -40°C

MINIMUM START-UP INPUT VOLTAGE



2.5 3.0

2.0
INPUT VOLTAGE (V)

MAX856/MAX857

vs. LOAD CURRENT

1 100

LOAD CURRENT (mA)

MAX856/MAX857

MAXIMUM OUTPUT CURRENT

vs. INPUT VOLTAGE

V

= 3.3V

OUT

2.01.5 2.5

INPUT VOLTAGE (V)



V

V

= 5.0V

OUT

3.0 3.5 4.0

OUT

= +85°C.

A

3.5

= 5V

V

OUT

= 3.3V

1.6

MAX856-08

1.4

1.2

1.0

0.8

0.6

0.4

QUIESCENT CURRENT (mA)

0.2

4.0



0

1.4

MAX856-06

1.3

1.2

1.1

1.0

START-UP INPUT VOLTAGE (V)

0.9

0.8

100

90

MAX856-13

80
70
60
50
40
30

LOAD CURRENT (mA)

20
10

0

1.5

0.1 10

1.0

4 _______________________________________________________________________________________

MAX858/MAX859

NO LOAD BATTERY CURRENT

vs. INPUT VOLTAGE



= +85°C

T

A



= +25°C

T

A



= -40°C

T

A

MINIMUM START-UP INPUT VOLTAGE

V

OUT

INCLUDES ALL EXTERNAL
COMPONENT LEAKAGES.
CAPACITOR LEAKAGE
DOMINATES AT T
CAPS ARE SPRAGUE 595D


2.5 3.0

2.0
INPUT VOLTAGE (V)

MAX858/MAX859

vs. LOAD CURRENT

V

= 5V

OUT

1 100

LOAD CURRENT (mA)

MAX858/MAX859

MAXIMUM OUTPUT CURRENT

vs. INPUT VOLTAGE

= 3.3V

V

= 5.0V

OUT

2.0

1.5

2.5 3.0

INPUT VOLTAGE (V)

= +85°C.

A

3.5

3.5

MAX856-09

4.0

MAX856-07

MAX856-12

4.0

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

_____________________________Typical Operating Characteristics (continued)

(Circuits of Figure 2, TA= +25°C, unless otherwise noted.)

MAX856/MAX857

50µs/div

V

OUT

50mV/div

V

IN

V

OUT

50mV/div

V

IN

1V/div

LINE-TRANSIENT RESPONSE (5V MODE)

3V

2V

MAX856/MAX857

MAX859 LINE-TRANSIENT RESPONSE

3V
2V

2ms/div



V

OUT

50mV/div

I

LOAD

0mA to 100mA

LOAD-TRANSIENT RESPONSE (5V MODE)

VIN = 2.5V

MAX858/MAX859 LOAD-TRANSIENT RESPONSE

V

OUT

50mV/div

I

LOAD

0mA to 25mA

0

25

MAX856–MAX859

V

OUT

2V/div

V

SHDN

5V/div

MAX856 START-UP DELAY (5V MODE)

VIN = 2.5V, I

LOAD

= 100mA

_______________________________________________________________________________________

1ms/div

5ms/div

V

2V/div

V

SHDN

5V/div

VIN = 2.5V

2ms/div



MAX858/MAX859 START-UP DELAY (5V MODE)

OUT

VIN = 2.5V, I

LOAD

= 25mA

5ms/div



5

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

______________________________________________________________Pin Description

PIN

MAX856
MAX858

MAX856–MAX859

MAX857
MAX859

11

—2

2—

33

44

55

NAME

–S—H—D—N–

–

3/–5

FB

REF

LBO

LBI

OUT

GND

LX

Shutdown Input. When low, the entire circuit is off and V
forward voltage drop of the external Schottky rectifier.

Selects the output voltage; connect to GND for 5V output, and to OUT for 3.3V
output.

Feedback Input for adjustable-output operation. Connect to an external resistor voltage
divider between OUT and GND.

1.25V Reference Voltage Output. Bypass with 0.22µF to GND (0.1µF if there is no external
reference load). Maximum load capability is 250µA source, 20µA sink.

Low-Battery Output. An open-drain N-channel MOSFET sinks current when the voltage at
LBI drops below 1.25V.

Low-Battery Input. When the voltage on LBI drops below 1.25V, LBO sinks current.
If not used, connect to VIN.

Connect OUT to the regulator output. OUT provides bootstrap power to the IC.66
Power Ground. Must be low impedance; solder directly to ground plane.77
N-Channel Power-MOSFET Drain88

_______________Detailed Description

The MAX856–MAX859 combine a switch-mode regula­tor, N-channel power MOSFET, precision voltage refer­ence, and power-fail detector in a single monolithic
device. The MOSFET is a “sense-FET” type for best
efficiency, and has a very low gate threshold voltage to
ensure start-up with low battery voltages (0.8V typ).

A unique minimum-off-time, current-limited pulse-fre­quency modulation (PFM) control scheme is a key fea­ture of the MAX856 series (Figure 1). This scheme
combines the high output power and efficiency of a
pulse-width modulation (PWM) device with the ultra-low
quiescent current of a traditional PFM pulse-skipper.
There is no oscillator; at heavy loads, switching is
accomplished through a constant-peak-current limit in
the switch, which allows the inductor current to vary
between this peak limit and some lesser value. At light
loads, switching frequency is governed by a pair of
one-shots, which set a minimum off-time (1µs) and a
maximum on-time (4µs). The switching frequency
depends upon the load and the input voltage, and can
range up to 500kHz.

Operating Principle

PFM Control Scheme

FUNCTION

= VIN- VD,where VDis the

OUT

The peak switch current of the internal MOSFET power
switch is fixed at 500mA ±100mA (MAX856/MAX857)
or 125mA ±25mA (MAX858/MAX859). The switch’s on­resistance is typically 1Ω (MAX856/MAX857) or 4Ω
(MAX858/MAX859), resulting in a switch voltage drop
(VSW) of about 500mV under high output loads. The
value of VSWwill decrease with light current loads.

Conventional PWM converters generate constant-fre­quency switching noise, whereas the unique architec­ture of the MAX856–MAX859 produces variable-fre­quency switching noise. However, unlike conventional
pulse-skippers (where noise amplitude varies with input
voltage), noise in the MAX856 series does not exceed
the switch current limit times the filter-capacitor equiva­lent series resistance (ESR).

Voltage Reference

The precision voltage reference is suitable for driving
external loads, such as an analog-to-digital converter.
The voltage-reference output changes less than ±2%
when sourcing up to 250µA and sinking up to 20µA. If
the reference drives an external load, bypass it with

0.22µF to GND. If the reference is unloaded, bypass it
with at least 0.1µF.

6 _______________________________________________________________________________________

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

MAX856–MAX859

SHDN

3/5*

LBO

MINIMUM
OFF-TIME

MAXIMUM

ON-TIME

ONE-SHOT

ONE-SHOT

TRIG

ONE-SHOT

MAX856–MAX859

Q

S

Q

ONE-SHOT

F/F

R

CURRENT-LIMIT

TRIG

Q

COMPARATOR

LX

N

GND

OUT

*

FB**

*

ERROR COMPARATOR

N

LBI

LBI COMPARATOR

REFERENCE

REF

V

IN

V

OUT

**

**

*MAX856/MAX858 ONLY
**MAX857/MAX859 ONLY

Figure 1. Block Diagram

_______________________________________________________________________________________ 7

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

The 3/5 input is internally diode clamped to GND and

Logic Inputs and Outputs

OUT, and should not be connected to signals outside
this range. The SHDN input and LBO output (open­drain) are not clamped to V+ and can be pulled as high
as 7V regardless of the voltage at OUT. Do not leave

control inputs (3/5, LBI, or SHDN) floating.

__________________Design Procedure

For the MAX856/MAX858,you can select a 3.3V or 5V
output voltage under logic control, or by tying 3/–5to
GND or OUT. Efficiency is typically better than 80%
over a 2mA to 100mA (MAX856/MAX857) load range.
The device is internally bootstrapped, with power
derived from the output voltage (via OUT). When the

MAX856–MAX859

output is in 5V mode, the higher internal supply voltage
results in lower switch-transistor on-resistance, slightly
greater output power, and higher efficiency.
Bootstrapping allows the battery voltage to sag to 0.8V
once the system is started. Therefore, the battery volt­age ranges from (V
forward drop of the Schottky rectifier). If the battery volt­age exceeds the programmed output voltage, the out-

R3

5

R4

1

3

0.1µF

C3

Output Voltage Selection

+ VD) to 0.8V (where VDis the

OUT

V

IN

LBI

MAX856/MAX858



SHDN

REF

GND

7

C1*


OUT

LBO

47µH
L1

D1

1N5817

8

LX

R1

6

2

OUTPUT

3/5

SELECT

4

C2*

put will follow the battery voltage. This is acceptable in
many systems; however, the input or output voltage
must not be forced above 7V.

The MAX857/MAX859’s output voltage is set by two
resistors, R1 and R2 (Figure 2b), which form a voltage
divider between the output and FB. Use the following
equation to determine the output voltage:

V

OUT

= V

( _________ )

REF

R1 + R2

R2

where V

REF

= 1.25V.

To simplify resistor selection:

V
V

OUT
REF

R1 = R2 ( _______ - 1)

Since the input bias current at FB has a maximum value
of 100nA, large values (10kΩ to 300kΩ) can be used
for R1 and R2 with no significant accuracy loss. For 1%
error, the current through R1 should be at least 100
times FB’s bias current.

V

IN

C1*

R3

V

OUT

R4

C3

0.1µF

5

LBI

MAX857/MAX859



1

SHDN

3

REF

GND

7

OUT

LBO

47µH
L1

D1

1N5817

8

LX

R1

6

2

FB

4

R2

C2*

V

OUT

*C1 = C2 = 68µF FOR MAX856

C1 = C2 = 22µF FOR MAX858



Figure 2a. Standard Application Circuit—Preset Output
Voltage

8 _______________________________________________________________________________________

*C1 = C2 = 68µF FOR MAX857

C1 = C2 = 22µF FOR MAX859



Figure 2b. Standard Application Circuit—Adjustable Output
Voltage

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

The MAX856 series contains an on-chip comparator for
low-battery detection. If the voltage at LBI falls below
the regulator’s internal reference voltage (1.25V), LBO
(an open-drain output) sinks current to GND. The low­battery monitor’s threshold is set by two resistors, R3
and R4 (Figure 2). Set the threshold voltage using the
following equation:

V

R3 = R4 ( ______ - 1)

where V
detector and V

Since the LBI current is less than 100nA, large resistor
values (typically 10kΩ to 300kΩ) can be used for R3
and R4 to minimize loading of the input supply.

When the voltage at LBI is below the internal threshold,
LBO sinks current to GND. Connect a pull-up resistor of
10kΩ or more from LBO to OUT when driving CMOS
circuits. When LBI is above the threshold, the LBO out­put is off. If the low-battery comparator is not used,
connect LBI to VINand leave LBO open.

is the desired threshold of the low-battery

LBI

LBI

V

REF

is the internal 1.25V reference.

REF

Inductor Selection

An inductor value of 47µH performs well in most
MAX856–MAX859 applications. However, the inductance
value is not critical, and the MAX856–MAX859 will work
with inductors in the 10µH to 100µH range. Smaller
inductance values typically offer a smaller physical size
for a given series resistance, allowing the smallest
overall circuit dimensions. However, due to higher peak

Low-Battery Detection

inductor currents, the output voltage ripple (I
output filter capacitor ESR) also tends to be higher.
Circuits using larger inductance values exhibit higher
output current capability and larger physical dimen­sions for a given series resistance.

The inductor’s incremental saturation current rating
should be greater than the peak switch-current limit,
which is 500mA for the MAX856/MAX857, and 125mA
for the MAX858/MAX859. However, it is generally
acceptable to bias the inductor into saturation by as
much as 20%, although this will slightly reduce
efficiency.

The inductor’s DC resistance significantly affects effi­ciency. See the Efficiency vs. Load Current for Various
Inductors graph in the
See Tables 1 and 2 for a list of suggested inductor
suppliers.

Typical Operating Characteristics

PEAK

A 68µF, 10V, 0.85Ω, surface-mount tantalum (SMT)
output filter capacitor typically provides 50mV output
ripple when stepping up from 2V to 5V at 100mA
(MAX856/ MAX857). Smaller capacitors (down to 10µF
with higher ESRs) are acceptable for light loads or in
applications that can tolerate higher output ripple.
Values in the 10µF to 47µF range are recommended for
the MAX858/MAX859.

The equivalent series resistance (ESR) of both bypass
and filter capacitors affects efficiency and output rip­ple. The output voltage ripple is the product of the peak
inductor current and the output capacitor’s ESR. Use
low-ESR capacitors for best performance, or connect
two or more filter capacitors in parallel. Low-ESR, SMT
tantalum capacitors are currently available from
Sprague (595D series) and AVX (TPS series). Sanyo
OS-CON organic-semiconductor through-hole capaci­tors also exhibit very low ESR, and are especially useful
for operation at cold temperatures. See Table 1 for a list
of suggested capacitor suppliers.

Rectifier Diode

Capacitor Selection

For optimum performance, a switching Schottky diode
(such as the 1N5817) is recommended. Refer to Table
1 for a list of component suppliers. For low output
power applications, a PN-junction switching diode
(such as the 1N4148) will also work well, although its
greater forward voltage drop will reduce efficiency.

PC Layout and Grounding

The MAX856 series’ high-frequency operation makes
PC layout important for minimizing ground bounce and

x

noise. Keep the IC’s GND pin and the ground leads of
C1 and C2 (Figure 1) less than 0.2in (5mm) apart. Also
keep all connections to the FB and LX pins as short as
possible. To maximize output power and efficiency and
minimize output ripple voltage, use a ground plane and
solder the IC’s GND (pin 7) directly to the ground
plane.

.

MAX856–MAX859

_______________________________________________________________________________________ 9

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

Table 1. Component Suppliers

PRODUCTION

METHOD

See Table 2Surface Mount

Miniature
Through Hole

Sumida
RCH654-220

MAX856–MAX859

Renco

Low-Cost
Through Hole

COMPANY PHONE FAX

AVX USA: [phone] [phone]
CoilCraft USA: [phone] [phone]
Coiltronics USA: [phone] [phone]
Matsuo USA: [phone] [phone]
Motorola USA: [phone]

Murata-Erie USA: [phone] [phone]
Nichicon USA: [phone] [phone]

Nihon USA: [phone] [phone]

Renco
Sanyo [phone]

Sumida USA: [phone] [phone]

TDK USA: [phone] [phone]

United Chemi-Con USA: [phone] [phone]

RL 1284-22
CoilCraft

PCH-27-223

[phone]

Japan: 81-3-3494-7411 81-3-3494-7414
USA: [phone]
USA: [phone]

Japan: 81-7-2070-6306 81-7-2070-1174

Japan: 81-3-3607-5111 81-3-3607-5144

Japan: 03-3278-5111 03-3278-5358

CAPACITORSINDUCTORS

Matsuo 267 series
Sprague 595D series
AVX TPS series

Sanyo
OS-CON series
low-ESR organic
semiconductor

Maxim
MAXC001
150µF, low-ESR
electrolytic

Nichicon
PL series
low-ESR
electrolytic

United Chemi-Con
LXF series

[phone]

RECTIFIERS

Motorola MBR 0530
Nihon EC15QS02L

Motorola
1N5817

10 ______________________________________________________________________________________

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

Table 2. Surface-Mount Inductor Information

MANUFACTURER PART

Sumida CDR105B-470 47 0.14 1.0 5.0
Sumida CDR74B-470 47 0.27 0.8 4.5
Sumida CD43-470 47 0.85 0.540 3.2
Sumida CD43-220 22 0.38 0.760 3.2
Murata-Erie LQH4N220 22 0.94 0.320 2.6
Murata-Erie LQH4N470 47 1.5 0.220 2.6
Murata-Erie LQH1N220 22 3.1 0.85 1.8
TDK NLC322522T-220K 22 1.15 0.210 2.2
TDK NLC322522T-470K 47 2.25 0.150 2.2
Coiltronics CTX20-1 20 0.175 1.15 4.2
Coilcraft DT1608-223 22 0.16 0.500 3.2

INDUCTANCE

(mH)

__Ordering Information (continued)

PIN-PACKAGETEMP. RANGEPART

MAX858CSA

-55°C to +125°CMAX858MJA

MAX859CSA

-55°C to +125°CMAX859MJA

* Dice are tested at TA= +25°C only.

†

Contact factory for availability.

8 SO0°C to +70°C
8 µMAX0°C to +70°CMAX858CUA
Dice*0°C to +70°CMAX858C/D
8 SO-40°C to +85°CMAX858ESA
8 CERDIP
8 SO0°C to +70°C
8 µMAX0°C to +70°CMAX859CUA
Dice*0°C to +70°CMAX859C/D
8 SO-40°C to +85°CMAX859ESA
8 CERDIP

†

†

RESISTANCE

(W)

RATED CURRENT

(A)

___________________Chip Topography

SHDN

3/5 OR FB*

REF

LBO

LX

GND

OUT

LBI

HEIGHT

(mm)

MAX856–MAX859

0.084"

(2.1336mm)

0.058"

(1.4732mm)

*3/5 FOR MAX856/MAX858; FB FOR MAX857/MAX859.

TRANSISTOR COUNT: 357;
SUBSTRATE CONNECTED TO OUT.

______________________________________________________________________________________ 11

3.3V/5V or Adjustable-Output,
Step-Up DC-DC Converters

________________________________________________________Package Information

INCHES MILLIMETERS

DIM



A

A1

B
C
D
E
e
H
L

α

0.101mm

0.004 in

C

L

A

e

A1B

α

MIN

0.036

0.004

0.010

0.005

0.116

0.116

0.188

0.016
0°

MAX

MIN

0.044

0.91

0.008

0.10

0.014

0.25

0.007

0.13

0.120

2.95

0.120

2.95





0.198

0.026
6°



4.78

0.41
0°

MAX856–MAX859

E H

8-PIN µMAX

MICROMAX SMALL OUTLINE

PACKAGE

D

MAX

1.11

0.20

0.36

0.18

3.05

3.05

0.650.0256



5.03

0.66
6°

INCHES MILLIMETERS

DIM



D

A

0.101mm

e

A1

B

0.004in.

C

L

0°-8°

Narrow SO

HE

SMALL-OUTLINE

PACKAGE

(0.150 in.)

A1

DIM

A

B
C
E

e

H

L

PINS



D
D
D

MAX

MIN

0.069

0.053

0.010

0.004

0.019

0.014

0.010

0.007

0.157

0.150


0.244

0.228

0.050

0.016

INCHES MILLIMETERS

MIN

8

0.189

14

0.337

16

0.386

12 ______________________________________________________________________________________



MAX

0.197

0.344

0.394

MIN

1.35

0.10

0.35

0.19

3.80

5.80

0.40



MIN

4.80

8.55

9.80

1.270.050

MAX

1.75

0.25

0.49

0.25

4.00


6.20

1.27

MAX

5.00

8.75

10.00

21-0041A