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MAX1958

W-CDMA/N-CDMA Cellular Phone HBT PA Management ICs

Maxim Integrated 

W-CDMA/N-CDMA Cellular Phone HBT PA

Management ICs

3.4

3.0

1.0

0.4

0.0

0 30

300

600

PA SUPPLY CURRENT (mA)

Figure 3. Typical W-CDMA Power Amplifier Load Profile

SHDN2 may result in indeterminate logic levels, and

could adversely affect op-amp operation.

Driving Capacitive Loads

The MAX1958/MAX1959 op amp is unity-gain stable for

capacitive loads up to 470pF. Applications that require

a greater capacitive drive capability should use an iso-

lation resistor (RISO) between the output and the

capacitive load (Figure 5). Note that this alternative

results in a loss of gain accuracy because RISO forms a

voltage-divider with RLOAD.

Power-Supply Bypass

The power-supply voltage applied to VCC for the op

amp and temperature sensor in the MAX1958/

MAX1959 circuit is filtered from INP. Connect VCC to

INP through an RC network (R2 and C7 in Figure 4) to

ensure a quiet power supply.

Temperature Sensor

The temperature sensor provides information about the

MAX1958/MAX1959 die temperature. The voltage at

TOUT (VTOUT) is related to die temperature as follows:

VTOUT = (-4 × 10-6 × T2 ) + (-1.13 × 10-2 × T) + 1.8708V

For stable operation, bypass TOUT to AGND with at

least a 0.01µF capacitor.

Temperature Sensor Error Due to Die Self-Heating

When the 800mA converter and the op amp are both

operated at heavy load while the temperature sensor is

enabled, the indicated temperature at TOUT deviates

several degrees from the actual ambient temperature

due to die self-heating effects. At light loads, when die

self-heating is low, TOUT tends to be a good approxi-

mation of the ambient temperature. At heavier loads,

the die self-heating is appreciable; TOUT gives a good

approximation of the die temperature, which can be

several degrees higher than the ambient temperature.

Sensing Circuit Board and Ambient Temperature

Temperature sensors like those found in the

MAX1958/MAX1959 that sense their own die tempera-

Table 1. Recommended Inductors

MANUFACTURER

PART NO.

INDUCTANCE DC RESISTANCE

(µH)

(mΩ)

RATED DC MAX

CURRENT

(mA)

DIMENSIONS

LxWxH

(mm)

800mA Application

Sumida

CDRH3D16-4R7

4.7

80

Toko

972AS-4R7M = P5

4.7

220

700mA Application

Sumida

CMD4D11-4R7

4.7

166

Toko

976AS-4R7 = P5

4.7

320

400mA Application

Murata

LQH3C4R7M34

4.7

200

Sumida

CDRH2D11-4R7

4.7

170

300mA Application

Murata

LQH1C4R7M04

4.7

650

900

3.8 x 3.8 x 1.8

960

4.6 x 4.6 x 1.2

750

3.5 x 5.3 x 1.2

740

3.6 x 3.6 x 1.2

450

2.5 x 3.2 x 2

500

3.2 x 3.2 x 1.2

0.34

1.6 x 3.2 x 2

Note: Efficiency may vary depending upon the inductor’s characteristics. Consult the inductor manufacturer for saturation current ratings.

20 ______________________________________________________________________________________

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