ADP3405 Analog Devices, ADP3405 Datasheet - Page 9

• Manufacturer Part Number: ADP3405
• Description: GSM Power Management System
• Manufacturer: Analog Devices

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
• Reset Generator
• Buffered Precision Reference
• SIM Interface Logic Level Translation (3 V/5 V)
• SIM Voltage Supply
• Power-On/-Off Logic
• Undervoltage Lockout
Oscillator, Real-Time Clock)
600
500
400
300
200
100
0
10
TCXO
REF
VCCA
100
1 LI-ION
CHARGER
3 NIMH
INPUT
FREQUENCY – Hz
OR
DIGITAL AND
SIM GND
ANALOG GND
1k
10 F
100nF
PROCESSOR
10k
0.22 F
100nF
2.2 F
GSM
FULL LOAD
MLCC CAPS
R1
2.2 F
10
R2
100k
10
11
12
13
14
1
2
3
4
5
6
7
8
9
RESCAP
DGND
RESET
REFOUT
ANALOGON
VTCXO
VCCA
AGND
VBAT
VCC
PWRONKEY
PWRONIN
ROWX
CHRON
ADP3405
TSSOP-28
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
SIMPROG
RESETIN
°
SIMGND
DATAIO
SIMBAT
C maximum allowable junction temperature. Figure 3
SIMON
CLKIN
VRTC
CAP+
CAP–
VSIM
CLK
RST
I/O
JA
28
27
26
25
24
23
22
21
20
19
18
17
16
15
) of the ADP3405 is 62
10 F
100nF
10 F
100nF
GSM PROCESSOR
CLK TO SIM CARD
RST TO SIM CARD
I/O TO SIM CARD
PROCESSOR
SIM PINS
GSM
OF
BACK-UP
COIN CELL
°
C/W for 6-layer boards.
°
C ambient temperature.
ADP3405