MAX1958EV Kit

General Description

The MAX1958/MAX1959 evaluation (EV) kit demonstrates
an application circuit ideal for use with hetero-junction
bipolar transistor power amplifiers (HBT PA). The
MAX1958/MAX1959 application circuit features an
800mA DC-to-DC buck converter, an operational amplifier,
and a high-accuracy temperature sensor.

The high-efficiency, dynamically adjustable, pulse-width
modulated (PWM), DC-to-DC buck converter is opti-
mized to provide power to the HBT PA in N-CDMA and
W-CDMA cellular phones. The 1MHz PWM switching fre-
quency allows the use of small external components,
while skip mode reduces quiescent current to 190µA
with light loads. The buck regulator is dynamically con-
trolled to provide any fixed output voltage in the 0.75V to
3.4V (MAX1958) and 1V to 3.6V (MAX1959) ranges. The
DC-to-DC converter utilizes a low on-resistance internal
MOSFET switch and synchronous rectifier to maximize
efficiency and minimize external component count.

The built-in operational amplifier is used to provide full
bias control for the PA to maximize efficiency. The
amplifier has Rail-to-Rail

input/output capability,

800kHz gain-bandwidth product, and 120dB open-loop
voltage gain. An added feature of the amplifier is an
active output discharge in shutdown mode.

The precision temperature sensor measures tempera-
tures between -40°C and +125°C.

This fully tested EV kit comes with the MAX1958 IC
installed. The MAX1959 has an identical pinout
arrangement and can be evaluated on this board. To
evaluate the MAX1959, request a free sample of the
MAX1959 when ordering this evaluation kit.

Features

o Buck Converter

Dynamically Adjustable Output from 0.75V to
3.4V (MAX1958)
Dynamically Adjustable Output from 1V to
3.6V (MAX1959)
1MHz Fixed-Frequency PWM
800mA Guaranteed Output Current
130mV IC Dropout at 600mA Load
16% to 100% Duty-Cycle Operation
Low Quiescent Current

190µA (typ) in Skip Mode (MAX1958)
3mA (typ) in PWM Mode
0.01µA (typ) in Shutdown Mode

No External Schottky Diode Required

o Operational Amplifier

Active Output Discharge in Shutdown Mode
800kHz Gain-Bandwidth Product
120dB Open-Loop Voltage Gain (R

= 100k

)

5mA Rail-to-Rail Output

o Temperature Sensor

-40°C to +125°C Rated Temperature Range
Accurate Sensor, -11.64mV/°C Slope

Evaluates: MAX1958/MAX1959

MAX1958/MAX1959 Evaluation Kit

________________________________________________________________ Maxim Integrated Products

19-2775; Rev 0; 2/03

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.

Ordering Information

PART

TEMP RANGE

IC PACKAGE

MAX1958EVKIT

-40°C to +85°C

20 Thin QFN

Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.

Note: When contacting these component suppliers, please specify you are using the MAX1958/MAX1959.

Component Suppliers

SUPPLIER

COMPONENT

PHONE

WEBSITE

Kamaya

Resistors

260-489-1533

www.kamaya.com

Murata

Capacitors

770-436-1300

www.murata.com

Sumida

Inductors

81-03-3667-3381

www.sumida.com

Taiyo Yuden

Capacitors

408-573-4150

www.t-yuden.com

Evaluates: MAX1958/MAX1959

Required Equipment

The following equipment is required before beginning:

· Three 6V (at 1A) DC power supplies or batteries

· Digital multimeter (DMM)

· Temperature gauge

· Current meter (optional)

Quick Start

The MAX1958 application circuit is fully assembled and
tested. Follow these steps to verify board operation.

DC-to-DC Converter

1) Preset one DC power supply (PS1) to 2.6V. Turn off

the power supply.

2) Preset the second DC power supply (PS2) to 0.43V.

Turn off the power supply.

3) Verify that the shunt is in place at JU1 between

positions 2 and 3 for normal-mode operation.

4) Verify that there is no shunt at JU2.

5) Connect the positive lead of PS1 to the VIN pad and

connect the negative lead of PS1 to GND.

6) Connect the positive lead of PS2 to the ADJ pad

and connect the negative lead of PS2 to GND5.

7) Connect the positive lead of the DMM to VOUT and

connect the negative lead of the DMM to GND3.
This DMM measures the output voltage at VOUT.

8) Turn on both of the power supplies (PS1 first, then PS2).

9) Verify that the voltage at VOUT is 0.75V.

10) Gradually increase the PS1 output voltage up to

4.7V verifying that the output voltage at VOUT
remains at 0.75V. VOUT does not regulate to 0.75V
at input voltages above 4.7V due to the minimum
duty-cycle range.

11) Gradually increase the output of the PS2 power

supply up to 1.93V verifying that the output voltage
tracks the ADJ voltage at (1.76

ADJ

). When V

ADJ

is 1.93V, V

OUT

should be 3.4V.

12) With V

ADJ

set at 0.57V, gradually increase the output

voltage of PS1 to 5.5V verifying that the VOUT output
voltage remains at 1V.

13) Connect an 800mA load between VOUT and GND3.

14) Verify that the voltage at VOUT is 1V.

Operational Amplifier

MAX1958/MAX1959 Evaluation Kit

_______________________________________________________________________________________

Component List

DESIGNATION

QTY

DESCRIPTION

C1, C3

4.7µF

±10%, 6.3V ceramic

capacitors
Taiyo Yuden JMK212BJ475KG

C2, C7

0.1µF

±10%, 50V X7R ceramic

capacitors
Taiyo Yuden EMK107BJ104KA

C4, C8, C9, C10

Not installed

0.01µF ±10%, 50V X7R ceramic
capacitor
Taiyo Yuden UMK107 B103KZ

560pF

±5%, 50V SL ceramic

capacitor
Murata GRM1881X1H561J

C11

22pF ±5%, 50V SL ceramic
capacitor
Murata GRM1881X1H220J

C12

100pF ±5%, 50V SL ceramic
capacitor
Murata GRM1881X1H101J

JU1

Jumper, SIP3, 3-pin header
Digikey S1012-3-ND

JU2, JU3, JU4

Jumpers, SIP2, 2-pin headers
Digikey S1012-2-ND

4.7µH, 900mA power inductor
Sumida CDRH3D16-4R7

±5% resistor

6.8k

±5% resistor

12k

±5% resistor

9.1k

±5% resistor

R5, R9, R10

Not installed

R6, R7, R8

±5% resistors

R11

100

±5% resistor

None

BNC connectors
A/D Electronics 580-002-00

MAX1958ETP

1) Preset one DC power supply (PS1) to 2.6V. Turn off

the power supply.

2) Preset another DC power supply (PS3) to 1V. Turn

off the power supply.

3) Verify that there is no shunt across JU4.

4) Connect the positive lead of PS1 to the VIN pad and

connect the negative lead of PS1 to the GND pad.

5) Connect the positive lead of PS3 to the IN+ pad and

connect the negative lead of PS3 to the GND4 pad.

6) Connect the positive lead of the DMM to AOUT.

Connect the negative lead of the DMM to GND1.
The DMM now measures the output voltage, AOUT.

7) Turn on the power supplies (PS1 first and then PS3).

8) Verify the output voltage at AOUT is 1.57V.

9) Gradually increase the output voltage of PS3 and

verify that the voltage at AOUT is (1.57

IN+

AOUT

cannot be higher than (V

- 25mV).

10) Gradually increase the output voltage of PS1 up to

5.5V verifying that the output voltage remains at
(1.57

IN+

Temperature Sensor

1) Preset a DC power supply (PS1) to 2.6V. Turn off

the power supply.

2) Verify that there is no shunt across JU3.

3) Connect the positive lead of PS1 to the VIN pad and

connect the negative lead of PS1 to the GND pad.

4) Place the input of the temperature gauge as close

to the IC as possible. For best results, solder a ther-
mocouple to the via connected to the exposed pad
on the back of the IC.

5) Turn on the power supply.

6) Measure the voltage at TOUT. Compare this voltage

with the output of the temperature gauge. See the
Temperature Sensor Operation section for the TOUT
voltage calculation.

Detailed Description

Setting the Output Voltage

The MAX1958's output voltage tracks the voltage at
ADJ. V

OUT

should regulate at 1.76

ADJ

for the

MAX1958 and 2

ADJ

- 0.8 for the MAX1959.

Temperature Sensor Operation

The temperature sensor provides information about the
MAX1958/MAX1959 die temperature. The voltage at
TOUT (V

TOUT

) is found as follows:

This equation can be approximated with the linear
function:

The temperature sensor provides accurate information
about the die temperature. Additional error in the temper-
ature output caused by die self-heating may exist. Refer
to the Temperature Sensor section in the MAX1958/
MAX1959 data sheet for more details.

Operational Amplifier Operation

The MAX1958 EV kit demonstrates the operational
amplifier in the MAX1958 in a noninverting configuration
with a gain of 1.57V/V. Resistors R2 and R3 can be
changed to alter the noninverting gain. The following
equation shows the relationship between R2 and R3 to
determine gain.

Jumper Settings

Jumper JU2/JU3/JU4 Functions

(Shutdown)

The MAX1958/MAX1959 feature a shutdown mode to
minimize the quiescent current. Place a shunt between
pins 1 and 2 on JU2 to shutdown the DC-to-DC converter.
Place a shunt between pins 1 and 2 on JU4 to shutdown
the operational amplifier. Place a shunt between pins 1
and 2 on JU3 to shutdown the temperature sensor.
Remove the shunts for normal operation.

Jumper JU1 Function (Mode Select)

The DC-to-DC converter contained in the MAX1958/
MAX1959 can be operated in two modes. Place a shunt
between pins 1 and 2 on JU1 to operate in forced-PWM
mode at all loads. Place a shunt between pins 2 and 3
on JU1 to operate in skip mode at light loads (<150mA)
and PWM mode at medium to heavy loads. Do not
leave JU1 unconnected.

AOUT

TOUT

-11 64

1 8778

TOUT

-4 10

-1.13 10

-6

-2

1 8708

Evaluates: MAX1958/MAX1959

MAX1958/MAX1959 Evaluation Kit

_______________________________________________________________________________________

Evaluates: MAX1958/MAX1959

MAX1958/MAX1959 Evaluation Kit

_______________________________________________________________________________________

MAX1958

OPEN

4.7

µF

OPEN

0.1

µF

C10
OPEN

C8
OPEN

VIN

2.6V TO 5.5V

GND

PWM

AGND

SHDN1

SHDN2

SHDN3

ADJ

EXPOSED PAD

IN+

4.7

µF

VOUT

GND3

AOUT

GND1

TOUT

GND2

9.1k

R11

100

C12
100pF

6.8k

R3
12k

C4
OPEN

C5
0.01

µF

C6
560pF

C7
0.1

µF

C11
22pF

JU1

JU4

JU3

JU2

R10

SHORT

ADJ

GND5

IN+

GND4

BNC CONNECTOR

PGND

OUT

AOUT

IN-

TOUT

COMP

REF

AGND

INP

4.7

µH

SUMIDA CDRH3D16-4R7

2
3

2
1

Figure 1. MAX1958/MAX1959 EV Kit Schematic

Part Number MAX1958EVKIT