___________________________MAX2233
Digital Gain Control
and Power Management
The MAX2233 responds to logic-level signals at the
device’s 2-bit DAC inputs, D0 and D1, placing the
device in shutdown mode or into one of three discrete
output power levels. See Table 2 for operating modes
and output power levels. Setting D0 and D1 to a logic-
level low places the device in shutdown mode and
reduces supply current to 0.2µA. The VGA, driver, and
output stage are off in shutdown mode, while the input
impedance is only slightly changed. Setting D0 and D1
to one of the other three modes adjusts the output
power to one of three discrete levels in 10dB steps.
Thermal Shutdown
The MAX2232/MAX2233 feature a thermal shutdown
mode that helps to protect the device from damage
when the die temperature becomes excessive. If the
temperature of the die exceeds the thermal shutdown
temperature, T
TH
, the VGA is forced into a low-gain
mode and output power is reduced to a minimum. After
the PA’s die temperature drops below T
TH
, the device
remains in thermal shutdown mode for the thermal shut-
down timeout period, t
TH
. A single capacitor, C
TSET
,
from TSET to ground sets t
TH
. The thermal shutdown
timeout period helps to limit device thermal cycling that
results if the source of the excessive temperature is not
removed. t
TH
is set by the value of C
TSET
.
Applications Information
Proper attention to voltage supply bypassing is essen-
tial for high-frequency RF circuit stability. Bypass V
CC
with 0.1µF, 10nF, and 100pF capacitors in parallel with
each other to ground. Use separate vias to the ground
plane for each of the bypass capacitors and minimize
trace length to reduce inductance. Use separate vias to
the ground plane for each ground pin. Use low-induc-
tance ground connections.
Decouple SHDN, CTRL, D0, and D1 with 0.1µF capaci-
tors to ground to minimize noise on the internal bias cell.
Use a series resistor (typically 100Ω) to further reduce
coupling of high-frequency signals into the control pins.
MAX2232/MAX2233
900MHz ISM-Band, 250mW Power Amplifiers
with Analog or Digital Gain Control
_______________________________________________________________________________________ 7
MODE
Standby > 2.0V
< 0.6V
V
SHDN
V
CTRL
X
≤ 0.4V
OUTPUT POWER
(P
RFIN
= 0dBm,
V
CC
= +3.6V)
< -35dBm
< -35dBm
Variable Gain > 2.0V
0.6V ≤ V
CTRL
< 2.2V
0dBm to +24dBm
Maximum Gain > 2.0V > 2.2V +24 dBm
Shutdown
Table 1. MAX2232 Operating Modes
X = Don’t care
Table 2. MAX2233 Operating Modes
Truth Table
MODE
Shutdown
Low Power 0
0
D1 D0
0
1
OUTPUT POWER
(P
RFIN
= 0dBm,
V
CC
= +3.6V)
< -35dBm
+6.5dBm
Medium Power 1 0 +15dBm
High Power 1 1 +24dBm
Functional Diagrams
