ADP3401

–9–

REV. 0

ANALOG GND

DIGITAL AND

SIM GND

1

2

3

4

5

6

7

8

9

10

11

12

13

14

2.2 F

100nF

28

27

26

25

23

22

21

20

19

18

17

16

15

ADP3401

100

10 F

R1

CHARGER INPUT

R2

BACKUP COIN CELL

10 F

SIM PIN OF

GSM PROCESSOR

2.2 F

10 F

24

0.22 F

100nF

10 F

CLK TO SIMCARD

RST TO SIMCARD

I/O TO SIM CARD

100nF

1 Li-ION OR

3 NiMH

CELLS

GSM

PROCESSOR

GSM

PROCESSOR

VBAT

VCC

PWRONKEY

ANALOGON

PWRONIN

ROWX

CHRON

VRTC

CAP–

SIMBAT

DATAIO

RESETIN

CLKIN

SIMGND

AGND

VCCA

REFOUT

VTCXO

DGND

RESCAP

CAP+

VSIM

CLK

SIMON

SIMPROG

RST

I/O

RESET

Figure 15. Typical Application Circuit

FREQUENCY – Hz

600

500

0

10

100k

100

1k

10k

400

300

200

100

FULL LOAD

MLCC CAPS

VCCA

TCXO

REF

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

(

θ

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

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