User Manual

APEX/APEX LT
Datasheet (Preliminary Rev 0.2) www.lsr.com Page 8 of 20
7 SIF Interface
The APEX and APEX LT modules provide access to the SIF module programming and debug
interface. Consult the EM250 and EM260 datasheets for further details on the following
features it provides
• Production Testing
• Firmware Download
• Product Control and Characterization
• XAP2b Code Development (APEX only)
8 Power Amplifier Regulator Control Line
Both the APEX and APEX LT modules include a separate 1.8V regulator for the power
amplifier bias to enable the consistent module output performance over the wide Vdd voltage
range of 2.1 – 3.6 volts. To prevent excessive sleep currents, this regulator needs to be
disabled when the module is put into sleep mode. An external pull up resistor population
option is provided on each module (R6) to allow the regulator to be constantly enabled. This
option will increase the sleep current of the module well above the specified values.
The following table provides the specifications for the regulator enable control line.
GPIO7 (APEX), VPA_EN (APEX LT)
Parameter Min Typ Max Unit
Regulator enable voltage 0.95 V
Regulator disable voltage 0.4 V
Enable line current (VEN = 0) 0.1
µA
Enable line current (VEN = Vdd) 10 µA
Turn on Time 250 µsec
On the APEX LT module the VPA_EN control must be provided by the host microprocessor. In
normal operation, the VPA_EN line must be set high. It must be set low when the module is put
into sleep mode in conjunction with putting the EM260 into deep sleep. Upon a module wake-
up the Turn on time requirement of 250µsec must be met prior to any transmission to allow the
module regulator to settle. The EM260 wake up time is separate from this value as this
250µsec requirement applies only to the external power amplifier.
On the APEX module, the regulator control line is brought to the module ports via GPIO7. The
host can drive this port as on the APEX LT module, but alternatively, the EM250 can use the
default serial digital function of GPIO7 which is as an external voltage regulator enable.
Please consult the EM250 datasheet for details on the operation of this function. Note that
both approaches preclude the use of the GPIO7 port for any other possible functions
including the use as the ADC3 input.
If the application does not put the module to sleep or if sleep current is not an issue, the
power amplifier regulator may be permanently enabled by tying the control line high. In this
setup, the sleep current will increase by 80µA over the value provided in section 5.2.