MAX2205(2002) 查看數據表（PDF） - Maxim Integrated

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MAX2205
(Rev.:2002)

RF Power Detectors in UCSP

Maxim Integrated 

RF Power Detectors in UCSP

Applications Information

The MAX2205–MAX2208 have internal termination

resistors for use with directional couplers. The applica-

tion circuit is shown in Figure 1. The output of the

detector goes to an op amp in an analog GSM power-

control scheme, or to an ADC in other systems such as

TDMA or discrete-time GSM power control.

The MAX2205 has high-input impedance for use with

high-value resistive tapping from a CDMA power ampli-

fier. This coupling method is the lowest cost and lowest

loss when used with an isolator. The application circuit

is shown in Figure 2. Connect CFILTER from the

MAX2205 output to GND to reduce residual amplitude

ripple. For IS98A reverse channel signal with peak-to-

avg ratio of 3.9dB, a 1.5nF capacitor gives 43mVP-P rip-

ple at 28dBm PA output and 390µs response time. For

CDMA2000 (pilot + DCCH) with peak-to-avg ratio of

5.4dB, the ripple is about 65mVP-P at 26dBm PA output.

The MAX2205 input impedance is listed in Table 1.

Layout

As with any RF circuit, the layout of the MAX2205–

MAX2208 circuits affects performance. Use a short

50Ω line at the input with multiple ground vias along the

length of the line. The input capacitor and resistor

should be placed as close to the IC as possible. The

VCC input should be bypassed as close as possible to

the IC with multiple vias connecting the capacitor to

ground. Refer to the MAX2205–MAX2208 EV kit data

sheet for a sample layout and details.

UCSP Reliability

The UCSP is a unique package that greatly reduces

board space compared to other packages. UCSP relia-

bility is integrally linked to the user’s assembly methods,

circuit board material, and usage environment. The user

should closely review these areas when considering

using a UCSP. This form factor might not perform equally

to a packaged product through traditional mechanical

reliability tests. Performance through operating life test

and moisture resistance remains uncompromised, as it

is determined primarily by the wafer-fabrication process.

Mechanical stress performance is a greater considera-

tion for a UCSP. UCSP solder-joint contact integrity must

be considered because the package is attached through

direct solder contact to the user’s PC board. Testing

done to characterize the UCSP reliability performance

shows that it is capable of performing reliably through

environmental stresses. Results of environmental stress

tests and additional usage data and recommendations

are detailed in the UCSP application note, which can be

found on Maxim’s website, www.maxim-ic.com.

Chip Information

TRANSISTOR COUNT: 344

COUPLER

PA

50Ω

TO ANT

PA

680Ω

ISOLATOR/

CIRCULATOR

TO ANT

MAX2206

MAX2207

MAX2208

PEAK

DETECTOR

TO ADC

OR OP AMP

Figure 1. MAX2206/MAX2207/MAX2208 Typical Application

Circuit

47pF

MAX2205

PEAK

DETECTOR

TO ADC

CFILTER

Figure 2. MAX2205 Typical Application Circuit

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