Maxim MAX8625, MAX8625A Datasheet

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.

General Description

The MAX8625A PWM step-up/down regulator is intend­ed to power digital logic, hard disk drives, motors, and
other loads in portable, battery-powered devices such
as PDAs, cell phones, digital still cameras (DSCs), and
MP3 players. The MAX8625A provides either a fixed

3.3V or adjustable output voltage (1.25V to 4V) at up to

0.8A from a 2.5V to 5.5V input. The MAX8625A utilizes
a 2A peak current limit.

Maxim’s proprietary H-bridge topology* provides a
seamless transition through all operating modes without
the glitches commonly seen with other devices. Four
internal MOSFETs (two switches and two synchronous
rectifiers) with internal compensation minimize external
components. A SKIP input selects a low-noise, fixed­frequency PWM mode, or a high-efficiency skip mode
where the converter automatically switches to PFM
mode under light loads for best light-load efficiency.
The internal oscillator operates at 1MHz to allow for a
small external inductor and capacitors.

The MAX8625A features current-limit circuitry that shuts
down the IC in the event of an output overload. In addi­tion, soft-start circuitry reduces inrush current during
startup. The IC also features True Shutdown

TM

, which
disconnects the output from the input when the IC is
disabled. The MAX8625A is available in a 3mm x 3mm,
14-pin TDFN package.

Applications

PDAs and Smartphones

DSCs and Camcorders

MP3 Players and Cellular Phones

Battery-Powered Hard Disk Drive (HDD)

Features

♦ Four Internal MOSFET True H-Bridge Buck/Boost
♦ Glitch-Free, Buck-Boost Transitions
♦ Minimal Output Ripple Variation on Transitions
♦ Up to 92% Efficiency

♦ 37µA (typ) Quiescent Current in Skip Mode

♦ 2.5V to 5.5V Input Range
♦ Fixed 3.3V or Adjustable Output

♦ 1µA (max) Logic-Controlled Shutdown

♦ True Shutdown
♦ Output Overload Protection
♦ Internal Compensation
♦ Internal Soft-Start
♦ 1MHz Switching Frequency
♦ Thermal-Overload Protection
♦ Small 3mm x 3mm, 14-Pin TDFN Package

MAX8625A

High-Efficiency, Seamless Transition,

Step-Up/Down DC-DC Converter

________________________________________________________________

Maxim Integrated Products

1

Ordering Information

MAX8625A

SKIP

IN

GND

FB

OUT

LX1

LX2

ON

INPUT

2.7V TO 5.5V

OUTPUT

3.3V

OFF

ON

PWM

SKIP

REF

Typical Operating Circuit

19-1006; Rev 1; 5/08

*

US Patent #7,289,119.

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

EVALUATION KIT

AVAILABLE

Note: The device is specified over the -40°C to +85°C extended
temperature range.

+

Denotes a lead-free package.

**

EP = Exposed pad.

PART

PIN­PACKAGE

TOP MARK

MAX8625AETD+

14 TDFN-EP**
(3mm x 3mm)

ABQ

MAX8625A

TDFN-EP

TOP VIEW

245

13 11 10

IN

GND

OUT

LX1

LX2

ON

1

+

14

INLX1

3

12

GNDLX2

6

9

OUTSKIP

7

8

REFFB

EP

EP = EXPOSED PAD.

Pin Configuration

MAX8625A

High-Efficiency, Seamless Transition,
Step-Up/Down DC-DC Converter

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= 3.6V, ON = SKIP = IN, FB = GND, V

OUT

= 3.3V, LX_ unconnected, C

REF

= C5 = 0.1µF to GND, Figure 4. TA= -40°C to +85°C.

Typical values are at T

A

= +25°C, unless otherwise noted.) (Note 2)

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.

IN, OUT, SKIP, ON to GND ......................................-0.3V to +6V

REF, FB, to GND...............................................-0.3V, (IN + 0.3V)

LX2, LX1 (Note 1).........................................................±1.5A

RMS

Continuous Power Dissipation (TA= +70°C)

Single-Layer Board (derate 18.5mW/°C

above T

A

= +70°C) ...................................................1482mW

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

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Range V

IN

2.5 5.5 V

UVLO Threshold UVLO VIN rising, 60mV hysteresis 2.20 2.49 V

Quiescent Supply Current, FPWM
Mode, Switching

I

IN

No load, V

OUT

= 3.2V 15 22 mA

Quiescent Supply Current, Skip
Mode, Switching

I

IN

SKIP = GND, no load 37 µA

Quiescent Supply Current, No
Switching, Skip Mode

I

IN

SKIP = GND, FB = 1.3V 35 45 µA

ON = GND, TA = +25°C 0.1 1

Shutdown Supply Current I

IN

TA = +85°C 0.2

µA

PWM mode, VIN = 2.5V to 5.5V 3.30 V

I

OUT

= 0 to 0.5A, VIN = 2.5V to 5.5V,

T

A

= -40°C to +85°C (Note 3)

-1 +1 %

SKIP mode, valley regulation value 3.28 V

Average skip voltage 3.285

Output Voltage Accuracy
(Fixed Output)

Load step +0.5A -3 %

Output Voltage Range
(Adjustable Output)

1.25 4.00 V

Maximum Output Current VIN = 3.6V 0.80 A

Soft-Start L = 3.3µH; C

OUT

= C3 + C4 = 44µF 250 mA/ms

Load Regulation I

OUT

= 0 to 500mA 0.1 %/mA

Line Regulation VIN = 2.5V to 5.5V 0.03 %/V

OUT Bias Current I

OUT

V

OUT

= 3.3V 3 µA

REF Output Voltage V

REF

VIN = 2.5V to 5.5V 1.244 1.25 1.256 V

REF Load Regulation I

REF

= 10µA 1 mV

FB Feedback Threshold V

FB

I

OUT

= 0 to full load, PWM mode; VIN = 2.5V

to 5.5V

1.244 1.25 1.258 V

Note 1: LX1 and LX2 have internal clamp diodes to IN, PGND and OUT, PGND, respectively. Applications that forward bias these

diodes should take care not to exceed the device's power-dissipation limits.

MAX8625A

High-Efficiency, Seamless Transition,

Step-Up/Down DC-DC Converter

_______________________________________________________________________________________ 3

Note 2: Devices are production tested at TA= +25°C. Specifications over the operating temperature range are guaranteed by

design and characterization.

Note 3: Limits are guaranteed by design and 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 an inductor value of 3.3µH. For the step-up mode, the idle-mode
transition varies with input to the output-voltage ratios.

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 3.6V, ON = SKIP = IN, FB = GND, V

OUT

= 3.3V, LX_ unconnected, C

REF

= C5 = 0.1µF to GND, Figure 4. TA= -40°C to +85°C.

Typical values are at T

A

= +25°C, unless otherwise noted.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

FB Dual-Mode Threshold V

FBDM

75 100 125 mV

VFB = 1.3V, TA = +25°C 0.001 0.1

FB Leakage Current I

FB

VFB = 1.3V, TA = +85°C 0.01

µA

ON, SKIP Input High Voltage V

IH

2.5V < VIN < 5.5V 1.6 V

ON, SKIP Input Low Voltage V

IL

2.5V < VIN < 5.5V 0.45 V

2.5V < VIN < 5.5V, TA = +25°C 0.001 1

ON Input Leakage Current I

IHL

TA = +85°C 0.01

µA

I

SKIPH

V

SKIP

= 3.6V 3 12

SKIP Input Leakage Current

I

SKIPL

V

SKIP

= 0V -2 -0.2

µA

Peak Current Limit I

LIMP

LX1 PMOS 1700 2000 2300 mA

Fault Latch-Off Delay 100 ms

Each MOSFET, TA = +25°C 0.05 0.1

MOSFET On-Resistance R

ON

Each MOSFET, VIN = 2.5V to 5.5V,
T

A

= -40°C to +85°C

0.2

Ω

Rectifier-Off Current Threshold I

LX1OFF

SKIP = GND 125 mA
SKIP = GND, load decreasing 100

Idle-Mode Current Threshold
(Note 4)

I

SKIP

Load increasing 300

mA

VIN = V

OUT

= 5.5V, V

LX1

= 0V to VIN,

V

LX2

= 0V to V

OUT

, TA = +25°C

0.01 1

LX1, LX2 Leakage Current I

LXLKG

TA = +85°C 0.2

µA

VIN = V

LX1

= V

LX2

= 0V, V

OUT

= 5.5V,

measure I (LX2), T

A

= +25°C

0.01 1

Out Reverse Current I

LXLKGR

TA = +85°C 0.5

µA

Minimum T

ON

T

ONMIN

25 %

OSC Frequency F

OSCPWM

850 1000 1150 kHz

Thermal Shutdown 15°C hysteresis +165 °C

Typical Operating Characteristics

(VIN= 3.6V, SKIP = GND, TA= +25°C, Figure 4, unless otherwise noted.)

MAX8625A

High-Efficiency, Seamless Transition,
Step-Up/Down DC-DC Converter

4 _______________________________________________________________________________________

EFFICIENCY vs. LOAD CURRENT

SKIP AND FPWM MODES

MAX8625A toc01

LOAD CURRENT (mA)

EFFICIENCY (%)

100101

10

20

30

40

50

60

70

80

90

100

0

0.1 1000

V

OUT

= 3.3V

V

IN

= 2.7V

3.0V,

3.3V,

3.6V,

4.2V,

5.0V
60

70

65

80

75

85

90

95

100

2.0 3.0 3.52.5 4.0 4.5 5.0 5.5 6.0

SKIP-MODE EFFICIENCY

vs. INPUT VOLTAGE

MAX8625A toc02

INPUT VOLTAGE (V)

EFFICIENCY (%)

100mA

300mA

500mA

V

OUT

= 3.3V
LOAD CURRENT = 100mA,
300mA, 500mA

EFFICIENCY vs. LOAD CURRENT

FPWM MODE (FIGURE 3)

MAX8625A toc03

LOAD CURRENT (mA)

EFFICIENCY (%)

100101

10

20

30

40

50

60

70

80

90

100

0

0.1 1000

V

OUT

= 2.8V

V

IN

= 2.7V

3.0V,

3.3V,

3.6V,

4.2V,

5.0V

EFFICIENCY vs. LOAD CURRENT

FPWM MODE (FIGURE 3)

MAX8625A toc04

LOAD CURRENT (mA)

EFFICIENCY (%)

100101

10

20

30

40

50

60

70

80

90

100

0

0.1 1000

V

OUT

= 3.45V

V

IN

= 2.7V

3.0V,

3.3V,

3.6V,

4.2V,

5.0V

OUTPUT VOLTAGE (3.3V INTERNAL FB)

vs. LOAD CURRENT

MAX8625A toc05

LOAD CURRENT (mA)

DEVIATION (%)

100101

-1.5

-1.0

-0.5

0

0.5

1.0

1.5

2.0

-2.0

0.1 1000

V

OUT

= 3.3V

T

A

= +25°C, TA = -40°C, TA = +85°C,

OUTPUT VOLTAGE (2.8V EXTERNAL FB)

vs. LOAD CURRENT (FIGURE 3)

MAX8625A toc06

LOAD CURRENT (mA)

DEVIATION (%)

100101

-1.5

-1.0

-0.5

0

0.5

1.0

1.5

2.0

-2.0

0.1 1000

V

OUT

= 2.8V

T

A

= +25°C, TA = -40°C, TA = +85°C

3.27

3.29

3.28

3.31

3.30

3.32

3.33

3.0 4.0 4.53.5 5.0 5.5 6.0

OUTPUT VOLTAGE vs. INPUT VOLTAGE

WITH INTERNAL FB RESISTORS

MAX8625A toc07

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

LOAD: 500mA, V

OUT

= 3.3V

T

A

= +25°C, TA = -40°C, TA = +85°C

2.75

2.77

2.76

2.79

2.78

2.81

2.80

2.82

3.0 4.0 4.53.5 5.0 5.5 6.0

OUTPUT VOLTAGE vs. INPUT VOLTAGE

WITH EXTERNAL FB RESISTORS

MAX8625A toc08

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

LOAD: 500mA, V

OUT

= 2.8V

T

A

= +25°C, TA = -40°C, TA = +85°C (FIGURE 3)

SUPPLY CURRENT vs. INPUT VOLTAGE

WITH NO LOAD

MAX8625A toc09

INPUT VOLTAGE (V)

SUPPLY CURRENT (mA)

5.55.04.54.03.53.02.5

0.1

1

10

100

0.01

2.0 6.0

NO LOAD V

OUT

= 3.3V

FPWM MODE

Typical Operating Characteristics (continued)

(VIN= 3.6V, SKIP = GND, TA= +25°C, Figure 4, unless otherwise noted.)

MAX8625A

High-Efficiency, Seamless Transition,

Step-Up/Down DC-DC Converter

_______________________________________________________________________________________

5

0

200

100

400

300

600

500

700

900

800

1000

2.0 3.0 3.52.5 4.0 4.5 5.0 5.5 6.0

MAXIMUM LOAD CURRENT

vs. INPUT VOLTAGE

MAX8625A toc10

INPUT VOLTAGE (V)

MAXIMUM LOAD CURRENT (mA)

V

OUT

= 3.3V

1

μs/div

SWITCHING WAVEFORMS

V

IN

= 3V, LOAD = 500mA, V

OUT

= 3.3V

MAX8625A toc11

V

LX1

2V/div

V

OUT

50mV/div
(AC-COUPLED)

V

LX2

2V/div

I

LX

500mA/div

1

μs/div

SWITCHING WAVEFORMS

V

IN

= 3.3V, LOAD = 500mA, V

OUT

= 3.3V

MAX8625A toc12

V

LX1

2V/div

V

OUT

50mV/div
(AC-COUPLED)

V

LX2

2V/div

I

LX

500mA/div

1

μs/div

SWITCHING WAVEFORMS

V

IN

= 3.6V, LOAD = 500mA, V

OUT

= 3.3V

MAX8625A toc13

V

LX1

2V/div

V

OUT

50mV/div
(AC-COUPLED)

V

LX2

2V/div

I

LX

500mA/div

10μs/div

SKIP MODE

V

IN

= 3V, LOAD = 20mA,

V

OUT

= 3.288V

MAX8625A toc14

CH1 = V

LX1

2V/div

V

OUT

20mV/div
(AC-COUPLED)

CH2 = V

LX2

2V/div

I

LX

500mA/div

1μs/div

FPWM MODE

V

IN

= 3V, LOAD = 20mA,

V

OUT

= 3.308V

MAX8625A toc15

V

LX1

2V/div

OUT

20mV/div
(AC-COUPLED)

V

LX2

2V/div

I

LX

500mA/div