Rainbow Electronics MAX1821 User Manual

General Description

The MAX1820/MAX1821 low-dropout, pulse-width-mod­ulated (PWM) DC-DC buck regulators are optimized to
provide power to the power amplifier (PA) in WCDMA
cell phones; however, they may be applied in many
other applications where high efficiency is a priority. The
supply voltage range is from 2.6V to 5.5V, and the guar­anteed output current is 600mA; 1MHz PWM switching
allows for small external components, while skip mode
reduces quiescent current to 180µA with light loads.

The MAX1820 is dynamically controlled to provide vary­ing output voltages from 0.4V to 3.4V. The circuit is
designed such that the output voltage settles in <30µs
for a full-scale change in voltage and current. The
MAX1821 is set with external resistors to provide any
fixed output voltage in the 1.25V to 5.5V range.

The MAX1820/MAX1821 include a low on-resistance
internal MOSFET switch and synchronous rectifier to
maximize efficiency and minimize external component
count; 100% duty-cycle operation allows for low dropout
of only 150mV at 600mA load, including the external
inductor resistance. The devices are offered in 10-pin
µMAX and tiny 3✕ 4 chip-scale (UCSP™) packages.

________________________Applications

WCDMA Cell Phone Power Amplifiers
PDA, Palmtop, and Notebook Computers
Microprocessor Core Supplies
Digital Cameras
PCMCIA and Network Cards
Hand-Held Instruments

Features

♦ Dynamically Adjustable Output from 0.4V to 3.4V

(MAX1820)

♦ Programmable Output from 1.25V to 5.5V

(MAX1821)

♦ SYNC to 13MHz External Clock (MAX1820X)

♦ SYNC to 19.8MHz External Clock (MAX1820Y)

♦ NO SYNC, Internal 1MHz Oscillator (MAX1820Z)

♦ Low Quiescent Current

180µA (typ) in Skip Mode

0.1µA (typ) in Shutdown Mode

♦ No External Schottky Diode Required

♦ 600mA Guaranteed Output Current

♦ 0% to 100% Duty-Cycle Operation

♦ 150mV Dropout at 600mA Load (Including R

DC

of External Inductor)

♦ µMAX or UCSP Packaging

MAX1820/MAX1821

WCDMA Cellular Phone 600mA

Buck Regulators

________________________________________________________________ Maxim Integrated Products 1

19-2011; Rev 2; 7/02

EVALUATION KIT

AVAILABLE

Ordering Information

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Pin Configurations appear at end of data sheet.

Typical Operating Circuits continued at end of data sheet.

SYNC

GND

SHDN

BATT

PGND

COMP

V

OUT

CONTROL

DAC

REF

LX

OUT

13MHz

OR

19.8MHz

MAX1820

SKIP

4.7µH

4.7µF

INPUT

2.6V TO

5.5V

DYNAMIC
OUTPUT

0.4V TO 3.4V

Typical Operating Circuits

*UCSP reliability is integrally linked to the user’s assembly methods, circuit board material, and environment. Refer to the UCSP

Reliability Notice in the UCSP Reliability section of this data sheet for more information.

UCSP is a trademark of Maxim Integrated Products, Inc.

Ordering Information continued at end of data sheet.

PART

MAX1820ZEBC*

MAX1820YEBC*

MAX1820XEBC*

MAX1820ZEUB

MAX1820YEUB

MAX1820XEUB

SYNC

FREQ (MHz)

No Sync

19.8

13

No Sync

19.8

13

OUTPUT VOLTAGE TEMP RANGE PIN-PACKAGE UCSP MARK

✕

4 UCSP AAB

✕

4 UCSP AAL

✕

4 UCSP AAM

Dynamic -40°C to +85°C3

Dynamic -40°C to +85°C3

Dynamic -40°C to +85°C3

Dynamic -40°C to +85°C 10 µMAX —

Dynamic -40°C to +85°C 10 µMAX —

Dynamic -40°C to +85°C10 µMAX —

MAX1820/MAX1821

WCDMA Cellular Phone 600mA
Buck Regulators

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

BATT, OUT (FB), SHDN, SYNC, SKIP,

REF to GND .......................................................-0.3V to +6.0V

PGND to GND .......................................................-0.3V to +0.3V

LX, COMP to GND...................................-0.3V to (V

BATT

+ 0.3V)

Output Short-Circuit Duration ............................................Infinite

Continuous Power Dissipation (T

A

= +70°C)

3

✕

4 UCSP (derate 10.4mW/°C above +70°C)............832mW

10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW

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

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

Storage Temperature Ranges

3

✕

4 UCSP ....................................................-40°C to +150°C

10-Pin µMAX ..................................................-65°C to +150°C

Solder Profile (UCSP) ......................................................(Note 1)

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

ELECTRICAL CHARACTERISTICS

(V

BATT

= 3.6V, SHDN = BATT, SKIP = SYNC = GND, V

REF

= 1.25V (MAX1820 only), TA= 0°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Note 2)

Note 1: For UCSP solder profile information, visit www.maxim-ic.com/1st_pages/UCSP.htm.

Input BATT Voltage V

Undervoltage Lockout

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Threshold

Quiescent Current I

V

UVLO

IN

Q

Quiescent Current in Dropout

Shutdown Supply Current I

SHDN

ERROR AMPLIFIER

OUT Voltage Accuracy
(MAX1820)

OUT Input Resistance
(MAX1820)

V

R

OUT

OUT

V

rising, 1% hysteresis 2.20 2.35 2.55 V

BATT

SKIP = GND (MAX1820Z/MAX1821) 180 300
SKIP = BATT, no switching 450 2000

SKIP = GND (MAX1820Y, MAX1820X, and

MAX1821X)

SKIP = BATT, 1MHz switching 3300
SKIP = GND 530 1000
SKIP = BATT, no switching 550 1000
SHDN = GND 0.1 6 µA

V

= 1.932 ±0.005V, load = 0 to 600mA,

REF

SKIP = BATT or GND

V

= 0.227 ±0.005V, load = 0 to 30mA,

REF

SKIP = BATT, V

2.6 5.5 V

240 360

3.33 3.4 3.47

BATT

≤ 4.2V

0.35 0.40 0.45

250 400 kΩ

µA

µA

V

REF Input Current (MAX1820) I

FB Voltage Accuracy
(MAX1821)

FB Input Current (MAX1821) I

Transconductance g

REF

V

FB

FB

FB = COMP 1.225 1.25 1.275 V

V

= 1.4V 0.01 50 nA

FB

m

30 50 85 µS

0.1 1 µA

COMP Clamp Low Voltage 0.2 0.45 1.0 V

COMP Clamp High Voltage 2.04 2.15 2.28 V

MAX1820/MAX1821

WCDMA Cellular Phone 600mA

Buck Regulators

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

BATT

= 3.6V, SHDN = BATT, SKIP = SYNC = GND, V

REF

= 1.25V (MAX1820 only), TA= 0°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Note 2)

CONTROLLER

P-Channel On-Resistance P

N-Channel On-Resistance N

Current-Sense Transresistance R

P-Channel Current-Limit
Threshold

P-Channel Pulse-Skipping
Current Threshold

N-Channel Current-Limit
Threshold

LX Leakage Current I

Maximum Duty Cycle duty

Minimum Duty Cycle duty

SYNC AND OSCILLATOR

SYNC Divide Ratio
(MAX1820X)

SYNC Capture Range
(MAX1820X)

SYNC Leakage Current
Frequency

SYNC Divide Ratio
(MAX1820Y)

SYNC Capture Range
(MAX1820Y)

Internal Oscillator Frequency
(MAX1820Z, MAX1821)

LOGIC INPUTS (SKIP, SHDN)

Logic Input High V

Logic Input Low V

Logic Input Current -1 0.1 1 µA

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

RDS

RDS

LX

I

SYNC

f

OSC

ILX = 180mA, V

ILX = 180mA, V

ILX = 180mA, V

ILX = 180mA, V

CS

Duty factor = 100% 0.75 1.2 1.55 A

SKIP = GND 0.04 0.13 0.24 A

SKIP = BATT -1.6 -0.85 -0.45
SKIP = GND 0.02 0.08 0.14

V

BATT

MAX

SKIP = GND 0

MIN

SKIP = BATT, V

S Y N C = si ne w ave, S Y N C i np ut = 200m V

S Y N C = si ne w ave, S Y N C i np ut = 800m V

SYNC = sine wave, AC-coupled,
SYNC input = 500mV

V

SYNC

V

SYNC

MAX1821X)

S Y N C = si ne w ave, S Y N C i np ut = 200m V

S Y N C = si ne w ave, S Y N C i np ut = 800m V

SYNC = sine wave, AC-coupled,
SYNC input = 500mV

SYNC = GND 0.8 1 1.2 MHz

IH

IL

= 3.6V 0.15 0.3

BATT

= 2.6V 0.2

BATT

= 3.6V 0.2 0.35

BATT

= 2.6V 0.3

BATT

0.25 0.50 0.75 V/A

= 5.5V, LX = GND or BATT -1 0.1 1 µA

100 %

= 4.2V

BATT

= 1V (MAX1820Z, MAX1821) -1 +1

= 1V (MAX1820X, MAX1820Y, and

P-P

P-P

P-P

P-P

P-P

P-P

P-P

13 13

13 13

10 13 16 MHz

-5 +5

18 18

18 18

15 19.8 21 MHz

1.6 V

10

0.4 V

Ω

Ω

A

%

Hz/Hz

µA

Hz/Hz

MAX1820/MAX1821

WCDMA Cellular Phone 600mA
Buck Regulators

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(V

BATT

= 3.6V, SHDN = BATT, SKIP = SYNC = GND, V

REF

= 1.25V (MAX1820 only), TA = -40°C to +85°C, unless otherwise noted.)

(Notes 2, 3)

Input BATT Voltage V

Undervoltage Lockout
Threshold

Quiescent Current I

Quiescent Current in Dropout

Shutdown Supply Current I

ERROR AMPLIFIER

OUT Voltage Accuracy
(MAX1820)

OUT Input Resistance
(MAX1820)

REF Input Current (MAX1820) I

FB Voltage Accuracy
(MAX1821)

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

IN

V

UVLO

Q

SHDN

V

OUT

R

OUT

REF

V

FB

V

BATT

SKIP = GND (MAX1820Z, MAX1821) 300

SKIP = GND (MAX1820X, MAX1820Y, and

MAX1821X)

SKIP = BATT, no switching 2000
SKIP = GND 1000
SKIP = BATT, no switching 1000
SHDN = GND 6 µA

V

REF

SKIP = BATT or GND

V

REF

SKIP = BATT, V

FB = COMP 1.225 1.275 V

rising, 1% hysteresis 2.15 2.55 V

= 1.932 ±0.005V, load = 0 to 600mA,

= 0.227 ±0.005V, load = 0 to 30mA,

≤ 4.2V

BATT

2.6 5.5 V

360

3.33 3.47

0.35 0.45

250 kΩ

1µA

µA

µA

V

FB Input Current (MAX1821) I

Transconductance g

COMP Clamp Low Voltage 0.2 1.0 V

COMP Clamp High Voltage 2.04 2.28 V

CONTROLLER

P-Channel On-Resistance P

N-Channel On-Resistance N

Current-Sense Transresistance R

P-Channel Current-Limit
Threshold

P-Channel Pulse-Skipping
Current Threshold

N-Channel Current-Limit
Threshold

FB

m

RDS

RDS

CS

V

= 1.4V 50 nA

FB

30 85 µS

ILX = 180mA, V

ILX = 180mA, V

Duty factor = 100% 0.75 1.55 A

SKIP = GND 0.04 0.24 A

SKIP = BATT -1.6 -0.45
SKIP = GND 0.01 0.14

= 3.6V 0.3 Ω

BATT

= 3.6V 0.35 Ω

BATT

0.25 0.75 V/A

A

MAX1820/MAX1821

WCDMA Cellular Phone 600mA

Buck Regulators

_______________________________________________________________________________________ 5

Note 2: Limits are 100% production tested at TA= +25°C for UCSP parts. Limits over the entire operating temperature range are

guaranteed by design and characterization but are not production tested.

Note 3: Specifications to -40°C are guaranteed by design and not subject to production test.

ELECTRICAL CHARACTERISTICS (continued)

(V

BATT

= 3.6V, SHDN = BATT, SKIP = SYNC = GND, V

REF

= 1.25V (MAX1820 only), TA = -40°C to +85°C, unless otherwise noted.)

(Notes 2, 3)

40

50

60

70

80

90

100

0 1.00.5 1.5 2.0 2.5 3.0 3.5 4.0

EFFICIENCY vs. OUTPUT VOLTAGE

(NORMAL MODE, V

IN

= 3.6V)

MAX1820/21 toc01

OUTPUT VOLTAGE (V)

EFFICIENCY (%)

R

LOAD

= 10Ω

R

LOAD

= 15Ω

R

LOAD

= 5Ω

40

50

60

70

80

90

100

0 1.00.5 1.5 2.0 2.5 3.0 3.5 4.0

EFFICIENCY vs. OUTPUT VOLTAGE

(PWM MODE, V

IN

= 3.6V)

MAX1820/21 toc02

OUTPUT VOLTAGE (V)

EFFICIENCY (%)

R

LOAD

= 10Ω

R

LOAD

= 15Ω

R

LOAD

= 5Ω

0

20

10

40

30

60

50

70

90

80

100

2.0 3.0 3.52.5 4.0 4.5 5.0 5.5 6.0

MAX1820/21 toc03

VIN (V)

EFFICIENCY (%)

EFFICIENCY vs. INPUT VOLTAGE

NORMAL MODE, R

LOAD

= 10Ω

V

OUT

= 1.8V

V

OUT

= 3.4V

V

OUT

= 0.4V

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

LX Leakage Current I

Maximum Duty Cycle duty

Minimum Duty Cycle duty

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

LX

MAX

V

BATT

SKIP = GND 0

MIN

SKIP = BATT, V

SYNC AND OSCILLATOR

SYNC Divide Ratio
(MAX1820X)

SYNC Capture Range
(MAX1820X)

SYNC Divide Ratio
(MAX1820Y)

SYNC Capture Range
(MAX1820Y)

SYNC Leakage Current I

SYNC

S Y N C = si ne w ave, S Y N C i np ut = 200m V

S Y N C = si ne w ave, S Y N C i np ut = 800m V

SYNC = sine wave, AC-coupled,
SYNC input = 500mV

S Y N C = si ne w ave, S Y N C i np ut = 200m V

S Y N C = si ne w ave, S Y N C i np ut = 800m V

SYNC = sine wave, AC-coupled,
SYNC input = 500mV

V

SYNC

V

SYNC

M AX 1821X )

Internal Oscillator Frequency
(MAX1820Z, MAX1821)

f

OSC

SYNC = GND 0.8 1.2 MHz

LOGIC INPUTS (SKIP, SHDN)

Logic Input High V

Logic Input Low V

IH

IL

Logic Input Current 1µA

= 5.5V, LX = GND or BATT -1 1 µA

100 %

= 4.2V 10

BATT

P-P

P-P

P-P

P-P

P-P

P-P

13 13

13 13

10 16 MHz

18

18

15 21 MHz

= IV ( M AX 1820Z , M AX 1821) -1

= IV ( M AX 1820X , M AX 1820Y , and

18

18

+1

-5 +5

%

Hz/Hz

Hz/Hz

µA

1.6 V

0.4 V

MAX1820/MAX1821

WCDMA Cellular Phone 600mA
Buck Regulators

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

90

0

1 100010010

MAX1821 EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V)

30

10

70

50

100

40

20

80

60

MAX1820/21 toc04

LOAD CURRENT (mA)

EFFICIENCY (%)

VIN = 5.0V

VIN = 3.6V

VIN = 5.0V

SKIP = GND (DASHED LINE)
SKIP = BATT (SOLID LINE)

VIN = 3.6V

90

0

1 100010010

MAX1821 EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 2.5V)

30

10

70

50

100

40

20

80

60

MAX1820/21 toc05

LOAD CURRENT (mA)

EFFICIENCY (%)

VIN = 5.0V

VIN = 3.6V

VIN = 3.6V

VIN = 5.0V

SKIP = GND (DASHED LINE)
SKIP = BATT (SOLID LINE)

VIN = 2.7V

VIN = 2.7V

90

0

1 100010010

MAX1821 EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 1.5V)

30

10

70

50

100

40

20

80

60

MAX1820/21 toc06

LOAD CURRENT (mA)

EFFICIENCY (%)

VIN = 5.0V

VIN = 3.6V

SKIP = GND (DASHED LINE)
SKIP = BATT (SOLID LINE)

VIN = 2.7V

0

40

20

80

60

120

100

140

0 200 300100 400 500 600

DROPOUT VOLTAGE vs. LOAD CURRENT

MAX1820/21 toc07

LOAD CURRENT (mA)

DROPOUT VOLTAGE (mV)

V

OUT

= 3.4V

RL = 57mΩ

0

2

1

5

4

3

8

7

6

9

2.0 3.0 3.52.5 4.0 4.5 5.0 5.5

SUPPLY CURRENT vs. SUPPLY VOLTAGE

MAX1820/21 toc08

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

V

OUT

= 1.5V

SKIP = BATT

20

80

60

40

120

100

200

180

160

140

220

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

SUPPLY CURRENT vs. SUPPLY VOLTAGE

MAX1820/21 toc09

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

V

OUT

= 1.5V

SKIP = GND

MAX1820/21 toc10

B

C

A

400ns/div

A: V

LX

, 5V/div
B: INDUCTOR CURRENT, 500mA/div
C: V

OUT

(AC-COUPLED), 5mV/div

HEAVY-LOAD SWITCHING WAVEFORMS

(V

IN

= 3.8V, V

OUT

= 3.4V,

I

LOAD

= 600mA, SKIP = BATT)

MAX1820/21 toc11

B

C

A

400ns/div

A: V

LX

, 5V/div
B: INDUCTOR CURRENT, 500mA/div
C: V

OUT

(AC-COUPLED), 5mV/div

MEDIUM-LOAD SWITCHING WAVEFORMS

(V

IN

= 3.8V, V

OUT

= 1.8V,

I

LOAD

= 300mA, SKIP = BATT)

MAX1820/21 toc12

B

C

A

400ns/div

A: V

LX

, 5V/div
B: INDUCTOR CURRENT, 100mA/div
C: V

OUT

(AC-COUPLED), 5mV/div

LIGHT-LOAD PWM SWITCHING WAVEFORMS

(V

IN

= 3.8V, V

OUT

= 0.45V,

I

LOAD

= 30mA, SKIP = BATT)