1. Verifying Power Domains in AeroFONE®
Subrata Roy
Senior Design Engr, Wireless
10/23/06
www.silabs.com

2. 2
Silicon Labs Portfolio
Products
8-bit, 8051,
Mixed-Signal MCUs
Fixed-Function
solutions
Products
FM Tuners
SiRX™ STB Receiver
XM Satellite Receiver
Products
Modem
Voice
Power
Timing
Products
Aero® Transceivers
AeroFONE®
Power Amplifier
RF Synthesizers
Core Capability
System on a Chip
Core Capability
Tuner and Demod
Integration
Core Capability
PLL and High
Voltage Expertise
Core Capability
RF design in
CMOS
MCUBroadcastWirelineWireless

3. 3
AeroFONE® based Design
Si4700 FM
Tuner
Si4300T Power
Amplifier
Si4905 AeroFONE:
TX, ABB, DBB, PMU,
Battery Charging
Circuitry
CP2102 USB to
UART Bridge

4. 4
AeroFONE® Power domains
♦ Motivations for Multiple Power Domains
Power Saving : power what you need
Power Saving : power as much as you need;
Voltage scaling for different operating modes
Backbias RAM, powerdown ROM
Different voltages needed by the function
Noise isolation
♦ Voltage Regulators
Vpermanent
Vgpio
Vext_memory
Vcore (Linear regulator, DCDC regulator)
Vanalog
VRF
Vcustom_digital1
Vcustom_digital2

5. 5
Power Control Feedback loop
Voltage
Regulators
Power
domains
Battery
♦ The chip controls its power
♦ Make sure it is not stuck in a bad state; e.g., waiting for input through an
un-powered path while powering-up
control status
P_ctl
Vdd

6. 6
Power Verification-1
♦ Specify
Map blocks to Power domain
Reset & clocks
Voltage modes, dynamic operating modes (load current)
input power domains, output power domains
pre-power domains : domains powered up before this block
post-power domains: domains powered after this block is powered
up
♦ Design :
RTL: signal connectivity
Interface Cells between power domains (level shifters, logic & noise
isolators) have explicit supply pins; these cells are custom designed
Analog components have explicit supply pins

7. 7
Power Verification-2
♦ Static Verification: Checks conditions independent of
stimulus; assuming specified constraints
all inputs of the domain are defined
Every domain can be reset at power up
Correct level shifting
All outputs to post-power domains are at 0 during ramp-up
Lot of painful scripting & reviews
♦ Dynamic Verification : functional operation of the device
exercising different power domains & power modes
All possible power up sequences
All possible sequences of power modes
Use AMS methodology

8. 8
Assertions
♦ Check that the system is always in valid system power
states
♦ Check that a transition from 1 valid system power state to
another valid system power state satisfies all necessary
conditions
♦ Examples
If Vext_memory is in low power mode then no access to memory
If Vgpio is in low power mode then no access to gpio pins except for
some keypad pins

9. 9
Power Verification-3
♦ Power Goals
♦ Design Level: Characterize Power usage of different blocks
in different modes
♦ System Level: Use information from Power Characterization
to build system level power models
Example: DRX2 : 8 slots of p1-mode, 2 slots of p2-mode out of 816
slots

10. 10
Modeling
♦ The quality of dynamic verification depends on modeling
♦ Interface Cells: level shift, logic & noise isolators
Voltage levels of power supply pins are modeled in Verilog-AMS
Any error in voltage levels is indicated by driving X to logic signals as
well as global error flags
Lump any effect of the digital load to the Voltage signals of the
interface cell
♦ All registers/outputs in a un-powered domain are forced to X
♦ The impact of power(vdd) on signals connected to an
interface cell are modeled within the Verilog-AMS model of
the interface cell
♦ Voltage Regulators
Model impact of controls signals on voltage outputs
Focus is on modeling the loop between Digital & analog domain
feedback loops within the analog are ignored

11. 11
Interface Cells- AMS model
♦ New disciplines are defined for hv/lv logic in AMS
♦ AMS connectrules define the electrical equivalent of
logic_hv/lv
♦ AMS automatically inserts connectors based on type
Logic_hv Logic_lv
LS_12.Cell
AMS-model
vdd2vdd1
logic_hv_to_electrical connector
electrical_to_logic_lv connector

12. 12
Summary
♦ Static Verification is well defined but requires lot of adhoc
scripting – standardization will have big impact here
♦ Dynamic verification
Better modeling of effects of system power states using AMS
For unmodeled effects we use constraints to restrict digital behavior
Example: Vgpio low power mode only allows access through some
kepad pins
Large number of combinations of power states and their sequencing
7 Regulators
3 power on events (power on key, RTC alarm, Charger insertion)
Some regulators completely hardware controlled (configured by input
pins); some are software controlled
Based on ordering of input events and subsequent software control there
are many possible sequences

13. 13
Wish List
♦ Efficient way to model effects of power modes/states
♦ Extension of our current modeling language (Verilog) but
more efficient than AMS
♦ Some Objections
different instances have different power contexts,
keep power information seperate from design
language constructs can address these issues (e.g., parameters,
vunit binding in systemverllog)