Maxim MAX8815A, MAX8815 Datasheet

General Description

The MAX8815A DC-DC step-up converter is a high-effi­ciency, low quiescent current, synchronous step-up
converter with True Shutdown™ and inrush-current lim­iting. The MAX8815A generates any output voltage
from 3.3V to 5V from a 2-cell NiMH/NiCd or a single-cell
Li+/Li polymer battery.

The MAX8815A uses two modes of operation. The first
mode of operation (normal) uses only 30µA (typ) quies­cent current and allows the converter to switch only
when needed at no load and light loads. Under moder­ate and heavy loads (typically above 90mA), the
MAX8815A uses a fixed-frequency pulse-width modula­tion (PWM) technique. This mode allows maximum effi­ciency at light loads. The second mode of operation is
a fixed-frequency forced-pulse-width modulation
(FPWM) mode where the converter switches at a fixed
frequency irrespective of the load. This mode allows for
easy noise filtering and lower output ripple.

The MAX8815A has a preset 2.5A current limit, allowing
500mA load at 1.8V input and 1A load at 2.5V input when
the output is set to 5V. Features include soft-start, which
limits inrush current during startup, True Shutdown, and
internal compensation. The MAX8815A is available in a
compact 10-pin, 3mm x 3mm TDFN package.

The MAX8815A evaluation kit can help shorten the time
required for system design.

Applications

DSC and DVC

Microprocessor/DSP Core Power

Cell Phones, PDAs, MP3 Players

Portable Handheld Devices

PCMCIA Cards

Features

♦ Up to 97% Efficiency with Internal Synchronous

Rectifier

♦ Low 30µA Quiescent Current

♦ Guaranteed 500mA Output Current at V

OUT

= 5V

from 1.8V Input

♦ Guaranteed 1A Output Current at 5V from 2.5V

Input

♦ Low-Noise Constant Frequency Operation (FPWM

Mode)

♦ 2MHz PWM Switching Frequency

♦ Preset (5V) or Adjustable Output

♦ Controlled Current in Soft-Start Limits Inrush

Current

♦ True Shutdown

♦ Internal Compensation

♦ Overload/Short-Circuit Protection

♦ 0.1µA Shutdown Current

♦ Thermal Shutdown

♦ Compact 10-Pin, 3mm x 3mm TDFN Package

MAX8815A

1A, 97% Efficiency, 30µA Quiescent Current

Step-Up Converter with True Shutdown

________________________________________________________________

Maxim Integrated Products

1

Ordering Information

19-4092; Rev 0; 5/08

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.

EVALUATION KIT

AVAILABLE

PART PIN-PACKAGE TOP MARK

MAX8815AETB+ 10 TDFN-EP* AUH

True Shutdown is a trademark of Maxim Integrated Products, Inc.

+

Denotes a lead-free package.

*

EP = Exposed pad.

Note: This device operates in the -40°C to +85°C extended
operating temperature range.

BATT

ON

SKIPB

LX

POUT

OUTS

FB

GND

INPUT VOLTAGE

1.2V TO 5.5V
OUTPUT VOLTAGE
5V UP TO 1A

MAX8815A

Typical Operating Circuit

TOP VIEW

SKIPB

OUTS

FB

ON

GND

1

2

3

4

5

10

98

7

6

POUT

POUT

LX

BATT

LX

MAX8815A

+

Pin Configuration

MAX8815A

1A, 97% Efficiency, 30µA Quiescent Current
Step-Up Converter with True Shutdown

2 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(V

OUTS

= V

POUT

= 5V, VON= V

BATT

= 3.6V, V

SKIPB

= GND, TA= -40°C to +85°C, typical values are at TA= +25°C, unless otherwise

noted. Limits are 100% production tested at T

A

= +25°C. Limits over the operating temperature range are guaranteed by design and

characterization.)

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.

PARAMETER CONDITIONS MIN TYP MAX UNITS

GENERAL

Operating Input Voltage Range 1.2 5.5 V

Minimum Startup Voltage 1.2 1.5 V

TA = +25°C 0.1 1

Shutdown Supply Current ON = GND

T

A

= +85°C 0.2

µA

No load, no switching, VFB = 1.28V 16 30

Supply Current

No load, switching (measured with external feedback);
V

POUT

= 5V

30

µA

OSCILLATOR

Switching Frequency 1.8 2.0 2.2 MHz

Maximum Duty Cycle 87.5 %

Output-Voltage Adjust Range 3.3 5.0 V

No load, TA = +25°C 1.255 1.265 1.275

FB Regulation Voltage

No load, T

A

= -40°C to +85°C (Note 3) 1.252 1.265 1.277

V

FB Load Regulation -7.5 mV/A

FB Line Regulation V

BATT

= 1.8V to 5V, I

POUT

= 0.5A -10 mV/D

TA =+25°C -50 -5 +50

FB Input Leakage Current

V

FB

= 1.28V, V

OUTS

=

V

POUT

= V

BATT

= 5.5V

T

A

= +85°C -5

nA

Idle Mode™ Trip Level (Note 4) 90 mA

ABSOLUTE MAXIMUM RATINGS

OUTS, BATT to GND ................................................-0.3V to +6V

POUT to OUTS ......................................................-0.3V to +0.3V

PGND (EP) to AGND .............................................-0.3V to +0.3V

FB to GND ................................................-0.3V to (V

OUT

+ 0.3V)

ON, SKIPB to GND ............-0.3V to the higher of (V

OUTS

+ 0.3V)

and (V

BATT

+ 0.3V)

LX Continuous Current (Note 1)..........................................2.75A

Continuous Power Dissipation (T

A

= +70°C)
10-Pin TDFN Single-Layer Board (derate 18.5 mW/°C

above +70°C)...........................................................1481.5mW

10-Pin TDFN Multilayer Board (derate 24.4 mW/°C

above +70°C)...........................................................1951.2mW

Junction-to-Case Thermal Resistance (θ

JC

) (Note 2)

10-Pin TDFN.................................................................8.5°C/W

Junction-to-Ambient Thermal Resistance (θ

JA

) (Note 2)

10-Pin TDFN..................................................................41°C/W

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature Range ............................-40°C to +150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

Note 1: LX has internal clamp diodes to PGND (EP) and VPWR, where VPWR is the internal power node and is the higher of BATT

and OUTS. Applications that forward bias these diodes should take care not to exceed the power-dissipation limits of the
device.

Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a 4-layer

board. For detailed information on package thermal considerations, visit www.maxim-ic.com/thermal-tutorial

.

Idle Mode is a trademark of Maxim Integrated Products, Inc.

MAX8815A

1A, 97% Efficiency, 30µA Quiescent Current

Step-Up Converter with True Shutdown

_______________________________________________________________________________________ 3

PARAMETER CONDITIONS MIN TYP MAX UNITS

DC-DC SWITCHES

p-Channel On-Resistance 0.14 0.25 Ω

n-Channel On-Resistance 0.1 0.17 Ω

n-Channel Current Limit 2.20 2.5 2.75 A

p-Channel Turn-Off Current 10 mA

TA = +25°C 0.1 2

OUT Leakage Current

V

LX

= VON = 0V, V

OUTS

=

V

POUT

= V

BATT

= 5.5V

T

A

= +85°C 0.2

µA

TA = +25°C 0.1 2

LX Leakage Current

V

LX

= 0V or 5.5V, V

OUTS

=

V

POUT

= V

BATT

= 5.5V,

V

ON

= 0V

T

A

= +85°C 0.2

µA

Soft-Start Interval Load dependent 6 ms

Overload Protection Fault Delay 16 ms

Startup into a Short Circuit 6ms

LOGIC INPUTS

ON Input Low Level V

OUTS

= V

POUT

= 0V and 1.5V < V

BATT

< 5.5V 0.5 V

ON Input High Level

V

OUTS

= V

POUT

= 0V and 1.5V < V

BATT

< 5.5V, VH is the

highter of V

POUT

and V

BATT

VH -

0.2V
(1.3V
max

)

V

SKIPB Input Low Level 3.3V < V

POUT

< V

OUT

< 5.5V 0.5 V

SKIPB Input High Level 3.3V < V

POUT

< V

OUT

< 5.5V 1.6 V

TA = +25°C 0.01 1

ON, SKIPB Input Leakage
Current

V

OUTS

= V

POUT

= V

BATT

=

5.5V

T

A

= +85°C 0.02

µA

Thermal Shutdown +167 °C

ELECTRICAL CHARACTERISTICS (continued)

(V

OUTS

= V

POUT

= 5V, VON= V

BATT

= 3.6V, V

SKIPB

= GND, TA= -40°C to +85°C, typical values are at TA= +25°C, unless otherwise

noted. Limits are 100% production tested at T

A

= +25°C. Limits over the operating temperature range are guaranteed by design and

characterization.)

Note 3: Guaranteed by design. Not production tested.
Note 4: The idle-mode current threshold is the transition point between fixed-frequency PWM operation and idle-mode operation. The

specification is given in terms of output load current for inductor values shown in the typical application circuits (Figure 1). The
idle-mode transition varies with input-to-output voltage ratio.

MAX8815A

1A, 97% Efficiency, 30µA Quiescent Current
Step-Up Converter with True Shutdown

4 _______________________________________________________________________________________

Typical Operating Characteristics

(V

OUTS

= V

POUT

= 5V, V

BATT

= VON= 3.6V, V

SKIPB

= GND.)

EFFICIENCY vs. LOAD

CURRENT, V

OUT

= 3.3V

MAX8815A toc01

OUTPUT CURRENT (mA)

EFFICIENCY (%)

100101

10

20

30

40

50

60

70

80

90

100

0

0.1 1000

VIN = 1.8V, SKIP
= 1.5V, SKIP

VIN = 3V, SKIP
= 2.5V, SKIP
= 3V, FPWM

VIN = 2.5V, SKIP
= 1.8V, SKIP
= 1.5V, FPWM

EFFICIENCY vs. LOAD

CURRENT, V

OUT

= 5V

MAX8815A toc02

OUTPUT CURRENT (mA)

EFFICIENCY (%)

100101

10

20

30

40

50

60

70

80

90

100

0

0.1 1000

VIN = 4.2V,
SKIP

SKIP
V

IN

= 3.6V,
= 3V,
= 2.4V,
= 1.8V,
= 1.5V

FPWM
V

IN

= 4.2V,
= 3.6V,
= 3V,
= 2.4V,
= 1.8V,
= 1.5V

0

0.4

0.2

0.8

0.6

1.2

1.0

1.4

1.2 2.21.7 2.7 3.2 3.7

MAXIMUM LOAD CURRENT

vs. INPUT VOLTAGE

MAX8815A toc03

INPUT VOLTAGE (V)

LOAD CURRENT (A)

V

OUT

= 5V

V

OUT

= 3.3V

4.80

4.90

4.85

5.00

4.95

5.05

5.10

0.1 101 100 1000

OUTPUT VOLTAGE

vs. LOAD CURRENT

MAX8815A toc04

LOAD CURRENT (mA)

OUTPUT VOLTAGE (V)

FPWM
SKIP

VIN = 3.6V,
= 3V,
= 2.5V,
= 1.8V,
= 1.5V

3.22

3.30

3.24

3.26

3.28

3.34

3.32

3.36

3.38

0.1 101 100 1000

OUTPUT VOLTAGE

vs. LOAD CURRENT

MAX8815A toc05

LOAD CURRENT (mA)

OUTPUT VOLTAGE (V)

VIN = 3.0V,
= 2.5V,
= 1.8V,
= 1.5V

FPWM
SKIP

0

2

1

4

3

5

6

1.2 3.22.2 4.2 5.2 6.2

OUTPUT VOLTAGE

vs. INPUT VOLTAGE

MAX8815A toc06

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)