ADP3401 Просмотр технического описания (PDF) - Analog Devices

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ADP3401

GSM Power Management System

Analog Devices 

ADP3401

600

500

VCCA

400 TCXO

FULL LOAD

MLCC CAPS

300

200

REF

100

0

10

100

1k

10k

100k

FREQUENCY – Hz

Figure 14. Output Noise Density

THEORY OF OPERATION

The ADP3401 is a power management chip optimized for use with

the AD20msp425 GSM baseband chipsets in handset applications.

Figure 1 shows a functional block diagram of the ADP3401.

The ADP3401 contains several blocks:

• Four Low Dropout Regulators (Digital, Analog, Crystal

Oscillator, Real-Time Clock)

• Reset Generator

• Buffered Precision Reference

• SIM Interface Logic Level Translation (3 V/5 V)

• SIM Voltage Supply

• Power-On/-Off Logic

• Undervoltage Lockout

These functions have traditionally been done as either a discrete

implementation or a custom ASIC design. ADP3401 combines

the benefits of both worlds by providing an integrated standard

product solution where every block is optimized to operate in a

GSM environment while maintaining a cost-competitive solution.

Figure 15 shows the external circuitry associated with the

ADP3401. Only a few support components, mainly decoupling

capacitors, are required.

Input Voltage

The input voltage range for ADP3401 is 3 V to 7 V and optimized

for a single Li-Ion cell or three NiMH/NiCd cells. The ADP3401

uses Analog Devices’ patented package thermal enhancement

technology, which allows 15% improvement in power handling

capability over standard plastic packages. The thermal impedance

(θJA) of the ADP3401 is 60°C/W. The charging voltage for a high

capacity NiMH cell can be as high as 5.5 V. Power dissipation

should be calculated at maximum ambient temperatures and

battery voltage in order not to exceed the 125°C maximum allow-

able junction temperature. Figure 16 shows the maximum total

LDO output current as a function of ambient temperature and

battery voltage.

However, high battery voltages normally occur only when the

battery is being charged and the handset is not in conversation

mode. In this mode there is a relatively light load on the LDOs.

A fully charged Li-Ion battery is 4.25 V, where the LDOs deliver

the maximum 240 mA up to the max 85°C ambient temperature.

CHARGER INPUT

1 Li-ION OR

3 NiMH

CELLS

R1

10␮F

GSM

PROCESSOR

R2

BACKUP COIN CELL

100nF

100nF

10␮F

SIM PIN OF

GSM PROCESSOR

1 VBAT

AGND 28

2 VCC

2.2␮F

3 PWRONKEY

4 ANALOGON

VCCA 27

REFOUT 26

RESET 25

100⍀ 2.2␮F

10␮F

5 PWRONIN

6 ROWX

7 CHRON

8 VRTC

ADP3401

VTCXO 24

DGND 23

RESCAP 22

CAP+ 21

0.22␮F

100nF

ANALOG GND

DIGITAL AND

SIM GND

9 CAP–

10 SIMBAT

VSIM 20

10␮F

CLK 19

CLK TO SIMCARD

11 DATAIO

12 RESETIN

SIMON 18

SIMPROG 17

GSM

PROCESSOR

13 CLKIN

RST 16

RST TO SIMCARD

14 SIMGND

I/O 15

I/O TO SIM CARD

Figure 15. Typical Application Circuit

REV. 0

–9–

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