Rainbow Electronics MAX8884Z User Manual

General Description

The MAX8884Y/MAX8884Z step-down converters with
dual low-dropout (LDO) linear regulators are intended to
power low-voltage microprocessors, DSPs, camera and
Wi-Fi modules, or other point of load applications in
portable devices. These ICs feature high efficiency with
small external component size. The step-down converter
output voltage is pin selectable between 1.2V and 1.8V,
and provides guaranteed output current of 700mA. The
2/4MHz hysteretic-PWM control scheme allows for tiny
external components and reduces no-load operating
current to 50μA. Two low quiescent current, low-noise
LDOs operate down to 2.7V supply voltage. Two switch­ing frequency options are available—MAX8884Y (2MHz)
and MAX8884Z (4MHz)—allowing optimization for small­est solution size or highest efficiency. Fast switching
allows the use of small ceramic 2.2μF input and output
capacitors while maintaining low ripple voltage. The
MAX8884Y/MAX8884Z have individual enables for each
output, maximizing flexibility.

The MAX8884Y/MAX8884Z are available in a 16-bump,
2mm x 2mm CSP package (0.7mm max height).

Applications

Cell Phones/Smartphones

PDA and Palmtop Computers

Portable MP3 and DVD Players

Digital Cameras, Camcorders

PCMCIA Cards

Handheld Instruments

Features

♦ Step-Down Converter

Pin-Selectable Output Voltage (1.2V/1.8V)
2MHz or 4MHz Switching Frequency
Low-Output Voltage Ripple
700mA Output Drive Capability
Simple Logic ON/OFF Control
Tiny External Components

♦ Low-Noise LDOs

2 x 300mA LDO
Pin-Selectable Output Voltage (LDO1)
Low 26µV

RMS

(typ) Output Noise
High 65dB (typ) PSRR
Simple Logic ON/OFF Control

♦ Low 0.1µA Shutdown Current
♦ 2.7V to 5.5V Supply Voltage Range
♦ Thermal Shutdown
♦ Tiny, 2mm x 2mm x 0.65mm CSP Package (4x4 Grid)

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters

with Dual 300mA LDO in 2mm x 2mm CSP

________________________________________________________________

Maxim Integrated Products

1

19-4418; Rev 0; 4/09

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.

Typical Application Circuit appears at end of data sheet.

AGND

PGND

REFBP

NC1

BUCK_EN

LX

LDO2

LDO2_EN

MAX8884Y
MAX8884Z

SEL

IN1A

IN2

IN1B

LDO1_EN

FB

LDO1

NC2

TOP VIEW

(BUMPS ON BOTTOM)

A1 A2 A3 A4

B1 B2 B3 B4

C1 C2 C3 C4

D1 D2 D3 D4

CSP

Pin Configuration

IN1A

LX

FB

2.2μH

AGND

BUCK_EN

LDO1_EN

LDO2_EN

IN2

BATT

2.7V TO 5.5V

BATT

2.7V TO 5.5V

BUCK ON/OFF

BUCK

1.2V/1.8V

REFBP

IN1B

LDO1 ON/OFF

LDO2 ON/OFF

LDO2

LDO1

V

LDO2

UP TO 300mA

V

LDO1

UP TO 300mA

PGND

SEL

2.2μF

2.2μF

BUCK/LDO1 VOLTAGE

SELECTION

MAX8884Y
MAX8884Z

Typical Operating Circuit

Ordering Information

Note: All devices are specified over the -40°C to +85°C operat­ing temperature range.

+

Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

PART PIN-PACKAGE

MAX8884YEREKE+T 16 CSP 2MHz

MAX8884ZEREKE+T 16 CSP 4MHz

SWITCHING

FREQUENCY

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters
with Dual 300mA LDO in 2mm x 2mm CSP

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

IN1A

= V

IN1B

= V

IN2

= V

LDO1_EN

= V

LDO2_EN

= V

BUCK_EN

= 3.6V. TA= -40°C to +85°C, typical values are at TA= +25°C, unless

otherwise noted.) (Note 1)

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.

IN1A, IN1B, IN2, REFBP to AGND ........................-0.3V to +6.0V

FB to PGND ...........................................................-0.3V to +6.0V

SEL, BUCK_EN to AGND...............-0.3V to (V

IN1A

/V

IN1B

+ 0.3V)

LDO1, LDO2, LDO1_EN, LDO2_EN

to AGND.................................................-0.3V to (V

IN2

+ 0.3V)

IN2 to IN1A, IN1B ..................................................-0.3V to +0.3V

AGND to PGND .....................................................-0.3V to +0.3V

IN1A, IN1B, LX Current .....................................................1A

RMS

Continuous Power Dissipation (TA= +70°C)

16-Bump CSP (derate 12.5mW/°C above +70°C) ..............1W

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

Junction Temperature......................................................+150°C

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

Bump Temperature*.........................................................+260°C

*

These ICs are constructed using a unique set of packaging techniques imposing a limit on the thermal profile used during board level
solder attach and rework. This limit permits only the use of the solder profiles recommended in the industry-standard specification,
JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection reflow. Preheating is required. Hand or wave soldering is not allowed.

INPUT SUPPLY

Input Voltage V

Input Undervoltage Threshold V

Shutdown Supply Current

No-Load Supply Current

THERMAL PROTECTION

Thermal Shutdown TA rising, 20°C typical hysteresis +160 °C

LOGIC CONTROL

Logic Input-High Voltage
(BUCK_EN, SEL, LDO1_EN,
LDO2_EN)

PARAMETER CONDITIONS MIN TYP MAX UNITS

, V

, V

IN1A

, V

IN1A

V

BUCK_ EN

V

LDO2_EN

V

BUCK_ EN

V

LDO1_EN

2.7V  V

IN1B

IN1B

IN1A

2.7 5.5 V

IN2

, V

rising, 180mV typical hysteres is 2.52 2.63 2.70 V

IN2

= V

LDO1_EN

=

= 0

= 0, I

= V

= V

LDO1

LDO2_EN

IN1B

= I

= 0, I

= V

TA= +25°C 0.1 4

T

= +85°C 0.1

A

= 0A 140 230 μA

LDO2

= 0A, no switching 50 80 μA

BUCK

 5.5V 1.3 V

IN2

μA

Logic Input-Low Voltage
(BUCK_EN, SEL, LDO1_EN,

2.7V  V

IN1A

= V

IN1B

= V

 5.5V 0.4 V

IN2

LDO2_EN)

Logic Input Current (BUCK_EN,
SEL, LDO1_EN, LDO2_EN)

V

= 0 or VIH= V

IL

IN1A

= 5.5V

TA = +25°C 0.01 1

= +85°C 0.1

T

A

FB

Buc k Con verter Output Voltage

FB Leakage Current

SEL = AGND, I

= V

V

SEL

IN1A

V

= V

V

IN1A

FB

IN1B

= 0

= 0A 1.18 1.22 1.24 V

BUCK

, I

= 0A 1.78 1.80 1.85 V

BUCK

= V

= 5.5V,

IN2

TA = +25°C 0.01 1

T

= +85°C 1

A

LX

On-Resistance

p-channel MOSFET switch, ILX = -40mA 0.18 0.30

n-channel MOSFET rectifier, I

= 40mA 0.15 0.25

LX

μA

μA



MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters

with Dual 300mA LDO in 2mm x 2mm CSP

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

IN1A

= V

IN1B

= V

IN2

= V

LDO1_EN

= V

LDO2_EN

= V

BUCK_EN

= 3.6V. TA= -40°C to +85°C, typical values are at TA= +25°C, unless

otherwise noted.) (Note 1)

Note 1: All devices are 100% production tested at T

A

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

design.

LX Leakage Current

p-Channel MOSFET Peak Current
Limit

n-Channel MOSFET Valley
Current Lim it

n-Channel MOSFET
Zero-Crossing Threshold

Min imum On-Time 0.07 μs

Minimum Off-Time 0.06 μs

Power-Up Delay From V

LDO1, LDO2

Output Voltage V

Output Voltage V

Output Current 300 mA

Current Lim it V

Dropout Voltage I

Line Regulation V

Load Regulation I

Power-Supply Rejection
V

LDO_

Output Noise

Output Capacitor for Stable
Operation

Shutdown Output Impedance V

Power-Up Delay From V

REFBP

REFBP Output Voltage 0  I

REFBP Supply Rejection V

PARAMETER CONDITIONS MIN TYP MAX UNITS

= V

V

IN1A

= 0

V

LX

= 0 0.8 1.0 1.2 A

V

LX

IN1B

= V

IN2

= 5.5V,

TA= +25°C 0.1 1

T

= +85°C 1

A

0.6 0.8 1.0 A

MAX8884Y_ 40

MAX8884Z_ 60

rising to VLX rising 120 250 μs

LDO_

LDO_

LDO_

LDO_

= 1mA;
= 100mA

= 1mA;
= 100mA

LDO_

= 30mA

LDO_

LDO_

= 30mA

LDO_

= 1.8V,

= 1.8V,

SEL = AGND 1.764 1.800 1.836

SEL = IN1_ 2.800

2.770 2.800 2.830 V

 2.5V) 70 200 mV

LDO_

= 100mA 2.4 mV

LDO_

65 dB

26 μV

< 10mA 0.1

< 200mA 1

LDO_

< 300mA 2.2

LDO_

= V

LDO2_EN

= 0 100 

rising to V

output ri sing 150 250 μs

LDO_

 1μA 1.237 1.250 1.263 V

/V

IN2

LDO1

LDO2

BUCK_ EN

V

= 5.5V, I

IN2

V

= 3.4V, I

IN2

V

= 5.5V, I

IN2

V

= 3.4V, I

IN2

= 0 310 450 750 mA

LDO_

= 100mA, TA= +25°C (V

LDO_

stepped from 3.5V to 5.5V, I

IN2

stepped from 50μA to 200mA 25 mV

LDO_

10Hz to 100 kHz, V

= 2.2μF, I

C

LDO_

10Hz to 100 kHz, V
C

= 2.2μF, I

LDO_

0 < I

LDO_

10mA < I

200mA < I

LDO1_EN

LDO_ EN

REFBP

stepped from 2.55V to 5.5V 0.2 5 mV

IN2

μA

mA

V

RMS

μF

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters
with Dual 300mA LDO in 2mm x 2mm CSP

4 _______________________________________________________________________________________

STEP-DOWN CONVERTER EFFICIENCY

vs. LOAD CURRENT, V

OUT

= 1.8V

MAX8884Y/Z toc01

LOAD CURRENT (mA)

EFFICIENCY (%)

10010

40

50

60

70

80

90

100

30

1 1000

MAX8884Y, VIN = 3.2V

= 3.6V
= 4.2V

MAX8884Z, V

IN

= 3.2V

= 3.6V
= 4.2V

STEP-DOWN CONVERTER EFFICIENCY

vs. LOAD CURRENT, V

OUT

= 1.2V

MAX8884Y/Z toc02

LOAD CURRENT (mA)

EFFICIENCY (%)

10010

40

50

60

70

80

90

100

30

1 1000

MAX8884Y, VIN = 3.2V

= 3.6V
= 4.2V

MAX8884Z, V

IN

= 3.2V

= 3.6V
= 4.2V

STEP-DOWN CONVERTER NO-LOAD

SUPPLY CURRENT vs. INPUT VOLTAGE

MAX8884Y/Z toc03

INPUT VOLTAGE (V)

SUPPLY CURRENT (μA)

54321

50

100

150

200

250

300

0

06

V

BUCK_EN

= V

IN

V

LDO1_EN

= V

LDO2_EN

= 0

VIN FALLING

VIN RISING

MAX8884Y

MAX8884Z

STEP-DOWN OUTPUT VOLTAGE vs. LOAD

CURRENT (VOLTAGE POSITIONING)

MAX8884Y/Z toc04

LOAD CURRENT (mA)

OUTPUT VOLTAGE (V)

10010

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

1.0
1 1000

SEL = IN1_

SEL = AGND

MAX8884Y STEP-DOWN CONVERTER

LIGHT LOAD SWITCHING WAVEFORMS

MAX8884Y/Z toc06

1μs/div

I

LX

V

OUT

V

LX

0A

2V/div

100mA/div

AC-COUPLED
10mV/div

0V

I

LOAD

= 50mA

MAX8884Z STEP-DOWN CONVERTER

HEAVY LOAD SWITCHING WAVEFORMS

MAX8884Y/Z toc07

200ns/div

I

LX

V

OUT

V

LX

0A

2V/div

500mA/div

AC-COUPLED
10mV/div

0V

I

LOAD

= 500mA

MAX8884Y STEP-DOWN CONVERTER

HEAVY LOAD SWITCHING WAVEFORMS

MAX8884Y/Z toc08

400ns/div

I

LX

V

OUT

V

LX

0A

2V/div

500mA/div

AC-COUPLED
10mV/div

0V

I

LOAD

= 500mA

Typical Operating Characteristics

(VIN= V

IN1A

= V

IN1B

= V

IN2

= 3.6V, V

BUCK

= 1.2V, V

LDO1

= 1.8V, V

LDO2

= 2.8V, MAX8884YEVKIT, TA= +25°C, unless otherwise noted.)

MAX8884Z STEP-DOWN CONVERTER

LIGHT LOAD SWITCHING WAVEFORMS

MAX8884Y/Z toc05

V

OUT

V

AC-COUPLED
20mV/div

I

LX

LX

400ns/div

100mA/div

0A

2V/div

0V

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters

with Dual 300mA LDO in 2mm x 2mm CSP

_______________________________________________________________________________________

5

MAX8884Z STEP-DOWN CONVERTER

LINE TRANSIENT RESPONSE

MAX8884Y/Z toc12

10μs/div

I

LX

V

IN

V

OUT

0A

1V/div

200mA/div

AC-COUPLED
20mV/div

I

LOAD

= 500mA

4V 4V

3.5V

MAX8884Y STEP-DOWN CONVERTER

LOAD TRANSIENT

MAX8884Y/Z toc14

20μs/div

I

LX

V

OUT

I

OUT

0A

1.8V DC OFFSET
100mV/div

500mA/div

500mA/div

0A

500mA

10mA 10mA

_______________________________________________________________________________________ 5

Typical Operating Characteristics (continued)

(VIN= V

IN1A

= V

IN1B

= V

IN2

= 3.6V, V

BUCK

= 1.2V, V

LDO1

= 1.8V, V

LDO2

= 2.8V, MAX8884YEVKIT, TA= +25°C, unless otherwise noted.)

MAX8884Z STEP-DOWN CONVERTER

LOAD TRANSIENT

MAX8884Y/Z toc13

20μs/div

V

OUT

I

LX

I

OUT

0A

500mA/div

0A

500mA/div

1.8V DC OFFSET
100mV/div

10mA10mA

500mA

MAX8884Z STEP-DOWN CONVERTER

SOFT-START WAVEFORMS

MAX8884Y/Z toc09

40μs/div

I

IN1

V

OUT

I

LX

V

BUCK_EN

0A

2V/div

500mA/div

0A

200mA/div

0V

1V/div

0V

I

LOAD

= 500mA

MAX8884Y STEP-DOWN CONVERTER

LINE TRANSIENT RESPONSE

4V 4V

V

IN

V

OUT

3.5V

MAX8884Y/Z toc11

1V/div

AC-COUPLED
20mV/div

MAX8884Y STEP-DOWN CONVERTER

V

BUCK_EN

SOFT-START WAVEFORMS

V

OUT

I

IN1

I

LX

40μs/div

I

LOAD

MAX8884Y/Z toc10

= 500mA

1V/div

0V

200mA/div

0A

500mA/div

0A

2V/div

0V

I

LX

I

= 500mA

LOAD

10μs/div

200mA/div

0A

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters
with Dual 300mA LDO in 2mm x 2mm CSP

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VIN= V

IN1A

= V

IN1B

= V

IN2

= 3.6V, V

BUCK

= 1.2V, V

LDO1

= 1.8V, V

LDO2

= 2.8V, MAX8884YEVKIT, TA= +25°C, unless otherwise noted.)

LDO POWER SUPPLY

RIPPLE REJECTION, V

OUT

= 1.8V

MAX8884Y/Z toc18

FREQUENCY (kHz)

RIPPLE REJECTION (dB)

100100.1 1

10

20

30

40

50

60

70

80

0

0.01 1000

I

LDO

= 30mA

LDO2 DROPOUT VOLTAGE

vs. LOAD CURRENT

MAX8884Y/Z toc17

LOAD CURRENT (mA)

DROPOUT VOLTAGE (V)

25020015010050

50

100

150

200

250

0

0 300

LDO POWER SUPPLY

RIPPLE REJECTION, V

OUT

= 2.8V

MAX8884Y/Z toc19

FREQUENCY (kHz)

RIPPLE REJECTION (dB)

1001010.1

10

20

30

40

50

60

70

0

0.01 1000

I

LDO_

= 30mA

LDO1, LDO2 INPUT SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX8884Y/Z toc16

INPUT VOLTAGE (V)

SUPPLY CURRENT (μA)

54321

50

100

150

200

250

300

350

0

06

V

LDO1_EN

= V

LDO2_EN

= VIN,

V

BUCK_EN

= 0

MAX8884Y STEP-DOWN CONVERTER

SHUTDOWN WAVEFORMS

MAX8884Y/Z toc15

10μs/div

I

LX

V

OUT

V

BUCK_EN

0V

1V/div

0V

5V/div

500mA/div

0A

I

LOAD

= 500mA

LDO OUTPUT VOLTAGE

NOISE WAVEFORM, V

VN = 26.1μV
f = 100Hz to 100kHz, I

RMS

,

LDO_

400μs/div

OUT_

= 30mA

= 1.8V

MAX8884Y/Z toc20

MAX8884Y/MAX8884Z
LDO1 = 1.8 AT 30mA

= 3.6V

V

IN

50μV/div

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters

with Dual 300mA LDO in 2mm x 2mm CSP

_______________________________________________________________________________________

7_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(VIN= V

IN1A

= V

IN1B

= V

IN2

= 3.6V, V

BUCK

= 1.2V, V

LDO1

= 1.8V, V

LDO2

= 2.8V, MAX8884YEVKIT, TA= +25°C, unless otherwise noted.)

LDO1, LDO2 LOAD TRANSIENT RESPONSE

MAX8884Y/Z toc24

20μs/div

I

LDO1

V

LDO2

I

LDO2

V

LDO1

AC-COUPLED
10mV/div

AC-COUPLED
10mV/div

50mA/div

50mA/div

1mA 1mA

1mA 1mA

40mA

40mA

LDO1, LDO2 LINE TRANSIENT

MAX8884Y/Z toc23

10μs/div

V

LDO1

V

IN

V

LDO2

AC-COUPLED
5mV/div

AC-COUPLED
5mV/div

1V/div

I

LDO1

= I

LDO2

= 100mA

4V 4V

3.5V

LDO OUTPUT-NOISE SPECTRAL DENSITY

vs. FREQUENCY, V

10,000

1000

100

NOISE DENSITY (nV√(Hz))

I

= 30mA

LDO_

10

0.01 1000
FREQUENCY (kHz)

LDO_

= 1.8V

1001010.1

MAX884Y/Z toc21

LDO OUTPUT-NOISE SPECTRAL DENSITY

vs. FREQUENCY, V

10,000

1000

100

NOISE DENSITY (nV√(Hz))

I

= 30mA

LDO_

10

0.01 1000
FREQUENCY (kHz)

LDO_

= 2.8V

1001010.1

MAX884Y/Z toc22

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters
with Dual 300mA LDO in 2mm x 2mm CSP

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VIN= V

IN1A

= V

IN1B

= V

IN2

= 3.6V, V

BUCK

= 1.2V, V

LDO1

= 1.8V, V

LDO2

= 2.8V, MAX8884YEVKIT, TA= +25°C, unless otherwise noted.)

LDO1, LDO2 LOAD TRANSIENT

RESPONSE NEAR DROPOUT

I

LDO2

1mA 1mA

V

LDO2

I

LDO1

1mA 1mA

V

LDO1

40mA

40mA

V

20μs/div

MAX8884Y/Z toc25

50mA/div

AC-COUPLED
10mV/div

50mA/div

AC-COUPLED
10mV/div

= V

+ 200mV

IN2

LDO2

REFBP SOFT-START

V

REFBP

V

LDO1_EN

V

LDO1

C

REFBP

= 0.033μF

MAX8884Y/Z toc27

1V/div

0V

2V/div

0V

1V/div

0V

V

LDO1_EN

V

LDO2_EN

V

LDO1_EN

V

V

LDO1

V

LDO2

REFBP

V

LDO1

LDO1, LDO2 STARTUP

AND SHUTDOWN RESPONSE

=

REFBP SOFT-START

C

REFBP

400μs/div

= 0.15μF

MAX8884Y/Z toc26

MAX8884Y/Z toc28

2V/div
0V

2V/div
0V

2V/div
0V

1V/div

0V

2V/div
0V

1V/div

0V

100μs/div

100μs/div

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters

with Dual 300mA LDO in 2mm x 2mm CSP

_______________________________________________________________________________________ 9

Detailed Description

The MAX8884Y/MAX8884Z are designed to power the
subcircuits within a system. These ICs contain a high­frequency, high-efficiency step-down converter and two
LDOs. The step-down converter delivers 700mA with
either 1.2V or 1.8V selectable output voltage using SEL.
The hysteretic PWM control scheme provides extremely
fast transient response, while 2MHz and 4MHz switch­ing frequency options allow the trade-off between effi­ciency and the smallest external components. The
MAX8884Y/MAX8884Z linear regulators can be used to
power loads requiring a low output noise supply.

Step-Down Converter Control Scheme

A hysteretic PWM control scheme ensures high efficien­cy, fast switching, fast transient response, low-output
voltage ripple, and physically tiny external components.
The control scheme is simple: when the output voltage
is below the regulation threshold, the error comparator
begins a switching cycle by turning on the high-side
switch. This high-side switch remains on until the mini­mum on-time expires and output voltage is within regu­lation, or the inductor current is above the current-limit
threshold. Once off, the high-side switch remains off
until the minimum off-time expires and the output volt­age falls again below the regulation threshold. During

Pin Description

PIN NAME FUNCTION

A1 REFBP

A2 AGND Low-Noise Analog Ground. Connect to common ground plane.

A3 NC1 No Internal Connection. Connect NC1 to ground.

A4 PGND Power Ground for Step-Down Converter. Connect to common ground plane.

B1 LDO2

B2 BUCK_EN

B3 LDO2_EN

B4 LX Inductor Connection. Connect an inductor from LX to the output of the step-down converter.

C1 IN2

C2 SEL

C3, C4 IN1B, IN1A

D1 LDO1

D2 LDO1_EN

D3 NC2 No Internal Connection. Connect NC2 to ground.

D4 FB FB is Connected to the Internal Feedback Network

Reference Noise Bypass. Bypass REFBP to AGND with a 0.033μF ceramic capacitor to reduce noise
on the LDO outputs. REFBP is internally pulled to ground through a 1kΩ resistor during shutdown.

300mA LDO Regulator 2 Output. For 300mA application, bypass LDO2 with a 2.2μF ceramic capacitor
as close as possible to LDO2 and AGND. For low-output current capability, up to 10mA, an output
capacitor of 0.1μF is sufficient to keep the output voltage stable. LDO2 is internally pulled to ground
through a 100Ω resistor when this regulator is disabled.

Step-Down Converter Enable Input. Connect BUCK_EN to IN1_ or logic-high for normal operation.
Connect BUCK_EN to AGND or logic-low for step-down shutdown mode.

LDO2 Enable Input. Connect LDO2_EN to IN2 or logic-high for normal operation. Connect LDO2_EN to
AGND or logic-low for LDO2 shutdown mode.

Supply Voltage Input for LDO1, LDO2, and Internal Reference. Connect IN2 to a battery or supply
voltage from 2.7V to 5.5V. Bypass IN2 with a 4.7μF ceramic capacitor as close as possible to IN2 and
AGND. Connect IN2 to the same source as IN1A and IN1B.

Output Voltage Selection for LDO1 and Step-Down Converter. Connect to IN1_ or AGND for output
voltage selection. See Table 1.

Supply Voltage Input for Step-Down Converter. Connect IN1B and IN1A to a battery or supply voltage
from 2.7V to 5.5V. Bypass the connection of IN1B and IN1A with a 2.2μF ceramic capacitor as close as
possible to IN1B, IN1A, and PGND. IN1A
and IN1B to the same source as IN2.

300mA LDO Regulator 1 Output. For 300mA application, bypass LDO1 with a 2.2μF ceramic capacitor
as close as possible to LDO1 and AGND. For low-output current capability, up to 10mA, an output
capacitor of 0.1μF is sufficient to keep output voltage stable. LDO1 is internally pulled to AGND
through a 100Ω resistor when this regulator is disabled.

LDO1 Enable Input. Connect LDO1_EN to IN2 or logic-high for normal operation. Connect LDO1_EN to
AGND or logic-low for LDO1 shutdown mode.

and IN1B are internally connected together. Connect IN1A

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters
with Dual 300mA LDO in 2mm x 2mm CSP

10 ______________________________________________________________________________________

the off period, the low-side synchronous rectifier turns
on and remains on until the high-side switch turns on
again. The internal synchronous rectifier eliminates the
need for an external Schottky diode.

At inductor currents below 40mA (60mA), the MAX8884Y
(MAX8884Z) automatically switches to pulse-skipping
mode to improve light-load efficiency. Output voltage
ripple remains low at all loads, while the skip-mode
switching frequency remains ultrasonic down to 1mA
(typ) loads.

Voltage Positioning Load Regulation

The MAX8884Y/MAX8884Z step-down converters utilize
a unique feedback network. By taking a DC feedback
from the LX node through R1 in the

Block Diagram

, the
usual phase lag due to the output capacitor is
removed, making the loop exceedingly stable and
allowing the use of very small ceramic output capaci­tors. To improve the load regulation, resistor R3 is
included in the feedback (see the

Block Diagram

). This
configuration yields load regulation equal to half the
inductor’s series resistance multiplied by the load cur­rent. This voltage positioning load regulation greatly
reduces overshoot during load transients.

SEL Output Voltage Selection

SEL is used to determine the output voltage of the buck
converter and LDO1. See Table 1.

Shutdown Mode

Drive BUCK_EN to logic-low to place the MAX8884Y/
MAX8884Z step-down converter in shutdown mode. In
shutdown, the control circuitry, internal switching
MOSFET, and synchronous rectifier turn off and LX
becomes high impedance.

The LDOs are individually enabled. Connect LDO1_EN
and LDO2_EN to GND or logic-low to place LDO1 and
LDO2 in shutdown mode. In shutdown, the outputs of
the LDOs are pulled to ground through an internal
100Ω resistor.

When the step-down converter and all LDOs are in shut­down, the MAX8884Y/MAX8884Z enter a very low-power
state, where the input current drops to 0.1μA (typ).

Step-Down Converter Soft-Start

The MAX8884Y/MAX8884Z step-down converter uses
internal soft-start circuitry to limit inrush current at startup,
reducing transients on the input source. Soft-start is partic­ularly useful for supplies with high output impedance such
as Li+ and alkaline cells. See the soft-start waveforms in
the

Typical Operating Characteristics

.

Thermal Shutdown

Thermal shutdown limits total power dissipation in the
MAX8884Y/MAX8884Z. If the junction temperature
exceeds +160°C, thermal shutdown circuitry turns off
the MAX8884Y/MAX8884Z, allowing the ICs to cool.
The ICs turn on and begin soft-start after the junction
temperature cools by 20°C. This results in a pulsed out­put during continuous thermal-overload conditions.

Applications Information

Output Voltages

The MAX8884Y/MAX8884Z DC-DC step-down convert­er sets the BUCK and LDO1 output voltage based on
the state of SEL. See Table 1.

Contact the factory for other output voltage options.

LDO Dropout Voltage

The regulator’s minimum input/output differential (or
dropout voltage) determines the lowest usable supply
voltage. In battery-powered systems, this determines the
useful end-of-life battery voltage. Because the
MAX8884Y/MAX8884Z LDOs use a p-channel MOSFET
pass transistor, their dropout voltages are a function of
drain-to-source on-resistance (R

DS(ON)

) multiplied by the

load current (see the

Typical Operating Characteristics

).

Inductor Selection

The MAX8884Y operates with a switching frequency of
2MHz and utilizes a 2.2μH inductor. The MAX8884Z
operates with a switching frequency of 4MHz and uti­lizes a 1μH inductor. The higher switching frequency of
the MAX8884Z allows the use of physically smaller
inductors at the cost of lower efficiency. The lower
switching frequency of the MAX8884Y results in greater
efficiency at the cost of a physically larger inductor.
See the

Typical Operating Characteristics

for efficiency

graphs for both the MAX8884Y and the MAX8884Z.

Table 1. SEL Output Voltage Selection

VV

I load cu

R DC impedance of inductor

V

=−

BUCK BUCK NO LOA D

=

LOAD

=

DCR

__AAD

BUCK NO LO

__

rrrent

V or V dependin g o n SEL=12 18..

IR

×

LOAD DCR

2

BUCK CONVERTER

SEL

AGND 1.2 1.8

IN1_ 1.8 2.8

OUTPUT VOLTAGE

(V)

LDO1

OUTPUT VOLTAGE

(V)

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters

with Dual 300mA LDO in 2mm x 2mm CSP

______________________________________________________________________________________ 11

The inductor’s DC current rating only needs to match the
maximum load of the application because the
MAX8884Y/MAX8884Z feature zero current overshoot
during startup and load transients. For optimum transient
response and high efficiency, choose an inductor with
DC series resistance in the 50mΩ to 150mΩ range. See
Table 2 for suggested inductors and manufacturers.

Output Capacitor Selection

For the DC-DC step-down converter, the output capacitor
C

BUCK

is required to keep the output voltage ripple small

and ensure regulation loop stability. C

BUCK

must have low
impedance at the switching frequency. Ceramic capaci­tors with X5R or X7R dielectric are highly recommended
due to their small size, low ESR, and small temperature
coefficients. Due to the unique feedback network, the out­put capacitance can be very low. A 2.2μF ceramic capaci­tor is recommended for most applications. For optimum
load-transient performance and very low output ripple, the
output capacitor value can be increased.

For LDO1 and LDO2, the minimum output capacitance
required is dependent on the load currents. For loads
lighter than 10mA, it is sufficient to use a 0.1μF ceramic
capacitor for stable operation over the full temperature
range. For loads up to 200mA, an output capacitor of
1μF is sufficient for stable operation over the entire tem­perature range. Operating the LDO at maximum rated
current the LDO1 and LDO2 requires a 2.2μF ceramic
capacitor. Using larger output capacitors reduces out­put noise and improves load-transient response, stabili­ty, and power-supply rejection.

Note that some ceramic dielectrics exhibit large capaci­tance and ESR variation with temperature. With dielectrics
such as Z5U and Y5V, it is necessary to use 4.7μF or more
to ensure stability at temperatures below -10°C. With X7R
or X5R dielectrics, 2.2μF is sufficient at all operating tem­peratures. These regulators are optimized for ceramic
capacitors. Tantalum capacitors are not recommended.

Input Capacitor Selection

The input capacitor (C

IN1

) of the DC-DC step-down
converter reduces the current peaks drawn from the
battery or input power source and reduces switching
noise in the MAX8884Y/MAX8884Z. The impedance of
C

IN1

at the switching frequency should be kept very
low. Ceramic capacitors with X5R or X7R dielectric are
highly recommended due to their small size, low ESR,
and small temperature coefficients. A 2.2μF ceramic
capacitor is recommended for most applications. For
optimum noise immunity and low input ripple, the input
capacitor value can be increased.

For the LDOs, use an input capacitance equal to the
value of the sum of the output capacitance of LDO1 and

LDO2. Larger input capacitor values and lower ESR pro­vide better noise rejection and line transient response.

Note that some ceramic dielectrics exhibit large capaci­tance and ESR variation with temperature. With dielectrics
such as Z5U and Y5V, it may be necessary to use two
times the sum of the output capacitor value of LDO1 and
LDO2 (or larger) to ensure stability at temperatures below

-10°C. With X7R or X5R dielectrics, a capacitance equal
to the sum is sufficient at all operating temperatures.

Reference Noise

Bypass Capacitor Selection

The REFBP capacitor reduces the output noise of LDO1
and LDO2. A value of 0.033μF is sufficient for most appli­cations. This value can be increased up to 0.150μF with
some effect on the soft-start time of the LDOs. See the

Typical Operating Characteristics

for more information.
Do not use values greater than 0.150μF as this degrades
the performance of the internal reference voltage and has
a corresponding impact on all output voltages.

Ceramic capacitors with X5R or X7R dielectric are high­ly recommended due to their small size, low ESR, and
small temperature coefficients. Note that some ceramic
dielectrics exhibit large capacitance and ESR variation
with temperature. With dielectrics such as Z5U and
Y5V, it may be necessary to use two times the recom­mended value to achieve desired output noise perfor­mance at temperatures below -10°C. Tantalum
capacitors are not recommended.

Thermal Considerations

In most applications, the MAX8884Y/MAX8884Z do not
dissipate much heat due to their high efficiency. But in
applications where the MAX8884Y/MAX8884Z run at high
ambient temperature with heavy loads, the heat dissipat­ed may exceed the maximum junction temperature of the
part. If the junction temperature reaches approximately
+160°C, all power switches are turned off and LX and FB
become high impedance, and LDO1 and LDO2 are
pulled down to ground through an internal 100Ω resistor.

The MAX8884Y/MAX8884Z maximum power dissipation
depends on the thermal resistance of the IC package
and circuit board, the temperature difference between
the die junction and ambient air, and the rate of airflow.
The power dissipated in the device, P

DISS

, is:

where η

BUCK

is the efficiency of the DC-DC step-down

converter, and P

BUCK

is the output power of the DC-DC

step-down converter.

PP

DISS BUCK LDO IN LDO LDO IN LDO

⎛

=−

⎜

BUCK

η

⎝

⎞

1

IVV I VV

+−+ −

1

()( )

⎟

12 1 2 2 2

⎠

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters
with Dual 300mA LDO in 2mm x 2mm CSP

12 ______________________________________________________________________________________

Table 2. Suggested Inductors

MANUFACTURER SERIES

CB2016T

Tai yo Yuden

CB2518T

MIPF2520

FDK

MIPF2016

Murata LQH32C_53

D3010FB 1.0 0.20 1170

TOKO

Sumida

D2812C

D310F

D312C

CDRH2D09

CDRH2D11

INDUCTANCE

(μH)

1.0

2.2

2.2

4.7

1.0

1.5

2.2

1.0

2.2

1.0

2.2

1.2

2.2

1.5

2.2

1.5

2.2

1.2

1.5

2.2

1.5

2.2

3.3

ESR

()

0.09

0.13

0.09

0.13

0.05

0.07

0.08

0.11 1100

0.06

0.10

0.09

0.15

0.13

0.17

0.10

0.12

0.08

0.09

0.12

0.05

0.08

0.10

CURRENT RATING

(mA)

510

510
340

1500
1500
1300

1000

790

860
640

1230
1080

1290
1140

590
520
440

680
580
450

DIMENSIONS

(mm)

2.0 x 1.6 x 1.8
= 5.8mm

2.5 x 1.8 x 2.0 = 9mm

2.5 x 2.0 x 1.0
= 5mm

2.0 x 1.6 x 1.0

= 3.2mm

3.2 x 2.5 x 1.7

= 14mm

3.0 x 3.0 x 1.0
= 9mm

3.0 x 3.0 x 1.2

= 11mm

3.6 x 3.6 x 1.0

= 13mm

3.6 x 3.6 x 1.2

= 16mm

3.0 x 3.0 x 1.0
= 9mm

3.2 x 3.2 x 1.2

= 12mm

3

3

3

3

3

3

3

3

3

3

3

1.0

Coilcraft LPO3310

ELC3FN

Panasonic

ELL3GM

Hitachi KSLI-252010

1.5

2.2

1.0

2.2

1.0

2.2

1.5

2.2

0.07

0.10

0.13

0.08

0.12

0.07

0.10

0.070

0.100

1600
1400
1100

1400
1000

1400
1100

2200
1800

3.3 x 3.3 x 1.0

= 11mm

3.2 x 3.2 x 1.2

= 12mm

3.2 x 3.2 x 1.5

= 15mm

2.5 x 2.0 x 1.0
= 5mm

3

3

3

3

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters

with Dual 300mA LDO in 2mm x 2mm CSP

______________________________________________________________________________________ 13

The maximum allowed power dissipation, P

MAX

, is:

where (T

JMAX

- TA) is the temperature difference

between the MAX8884Y/MAX8884Z die junction and
the surrounding air, and θJAis the thermal resistance of
the junction through the PCB, copper traces, and other
materials to the surrounding air.

PCB Layout

High switching frequencies and relatively large peak
currents make the PCB layout a very important part of
design. Good design minimizes excessive EMI on the
feedback paths and voltage gradients in the ground
plane, resulting in a stable and well regulated output.
Minimize the ground loop formed by C

IN1

, C

BUCK

, and

PGND. To do this, connect C

IN1

close to IN1A/IN1B
and PGND. Connect the inductor and output capacitor
as close as possible to the IC and keep their traces
short, direct, and wide. Keep noisy traces, such as the
LX node, as short as possible. Connect AGND and
PGND to the common ground plane. Figure 1 illustrates
an example PCB layout and routing scheme.

Figure 1. Recommended PCB Layout

TT

()

P

MAX

J MAX A

=

−

_

θ

JA

REFBP

A1 A2 A3 A4

LDO2 BUCK_EN

B1 B2 B4

IN2

SEL

C1 C2 C3 C4

LDO1_ENLDO1

D1 D3 D4

3.8mm

LDO2

C

REFBP

C

LDO2

C

IN2

SEL

BUCK_EN

NC1AGND

LDO2_EN

B3

IN1B

LDO2_EN

PGND

LX

IN1A

FBNC2

GND

C

IN1

C

BUCK

LDO1_EN

D2

C

LDO1

L

BUCK

IN

LDO1

4.0mm

BUCK

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters
with Dual 300mA LDO in 2mm x 2mm CSP

14 ______________________________________________________________________________________

Block Diagram

IN1A

IN1B

SEL

REF

R7

C2

R6

PWM

ERROR AMP

PWM LOGIC

STEP-DOWN

CURRENT LIMIT

R1

C1

R2

R3

LX

PGND
FB

IN2

REFBP

AGND

LDO1_EN
LDO2_EN

SEL

BUCK_EN

REF

REFBP

CONTROL

LOGIC

REFBP

MAX8884Y

MAX8884Z

ERROR
AMP

ERROR
AMP

CURRENT LIMIT

LDO1_EN

SEL

CURRENT LIMIT

LDO2_EN

LDO1

R9

R8

R7

LDO2

R12

R11

R10

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters

with Dual 300mA LDO in 2mm x 2mm CSP

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________

15

© 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

16 CSP R162A2+1

21-0226

Package Information

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

2–4MHz

BUCK

FB

REF

LDO1

CONTROL

LX

2.2μH (MAX8884Y)

1.0μH (MAX8884Z)

PGND

IN1A

SEL

REFBP

AGND

LDO1

LDO2

IN2

GPIO
GPIO
GPIO

BASEBAND

PROCESSOR

CAMERA MODULE

CORE

DIGITAL

ANALOG

1.2V

IN1B

LDO2_EN

LDO1_EN

BUCK_EN

4.7μF

Li+

BATTERY

2.2μF

2.2μF

2.2μF

2.2μF

0.033μF

MAX8884Y
MAX8884Z

LDO2

Typical Application Circuit