ADP3405

–9–

REV. 0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

CHRON

ROWX

PWRONIN

ANALOGON

VCC

VBAT

VTCXO

RESET

AGND

VCCA

REFOUT

28

27

26

25

24

23

22

21

20

19

18

17

16

15

ADP3405

VRTC

CAP–

PWRONKEY

RESCAP

DGND

TSSOP-28

DIGITAL AND

SIM GND

ANALOG GND

SIM PINS

OF

GSM PROCESSOR

GSM

PROCESSOR

RST TO SIM CARD

I/O TO SIM CARD

CLK TO SIM CARD

10 F

100nF

BACK-UP

COIN CELL

100nF

GSM

PROCESSOR

CHARGER

INPUT

1 LI-ION

OR

3 NIMH

10 F

100nF

100nF

2.2 F

0.22 F

10

2.2 F

R1

R2

10 F

SIMBAT

DATAIO

RESETIN

CLKIN

SIMGND

CAP+

VSIM

CLK

SIMON

I/O

RST

SIMPROG

Figure 2. Typical Application Circuit

FREQUENCY – Hz

600

500

0

10

100k

100

1k

10k

400

300

200

100

FULL LOAD

MLCC CAPS

VCCA

TCXO

REF

TPC 13. Output Noise Density

THEORY OF OPERATION

The ADP3405 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 ADP3405.

The ADP3405 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. ADP3405 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 2 shows the external circuitry associated with the ADP3405.

Only a few support components, mainly decoupling capacitors,

are required.

Input Voltage

The input voltage range for ADP3405 is 3 V to 7 V and optimized

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

impedance (

θ

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

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