Datasheet
Table Of Contents
- FEATURES
- APPLICATIONS
- DESCRIPTION
- ELECTRICAL SPECIFICATIONS
- ABSOLUTE MAXIMUM RATINGS
- RECOMMENDED OPERATING CONDITIONS
- ELECTRICAL CHARACTERISTICS
- ADC MONITORING INTERVALS AND RESPONSE TIMES
- HARDWARE FAULT DETECTION LATENCY
- PMBus/SMBus/I2C
- I2C/SMBus/PMBus Timing Characteristics
- FUNCTIONAL OVERVIEW
- PMBus Interface
- Resistor Programmed PMBus Address Decode
- JTAG Interface
- Bias Supply Generator (Series Regulator Controller)
- Power On Reset
- External Reset
- Output Voltage Adjustment
- Analog Front End (AFE)
- Digital Compensator
- DPWM Engine
- Flexible Rail/Power Stage Configuration
- DPWM Phase Distribution
- DPWM Synchronization
- Phase Shedding at Light Current Load
- Phase Adding at Normal Current Load
- Output Current Measurment
- Output Current Balancing
- Overcurrent Detection
- Current Foldback Mode
- Input Voltage and Current Monitoring
- Temperature Monitoring
- Temperature Balancing
- Soft Start, Soft Stop Ramp Sequence
- Input UV Lockout
- Voltage Tracking
- Sequencing
- Fan Control
- Non-volatile Memory Error Correction Coding
- APPLICATION INFORMATION
Fan Control
+
1k31k0
1u
FAN-PWM
FAN-TACH
12V
FAN
33k2
0.1u
TIP31A
TS321
10k0
3.3V
Non-volatile Memory Error Correction Coding
APPLICATION INFORMATION
Calculation of Open Loop Gain Using the UCD9240
UCD9240
SLUS766C – JULY 2008 – REVISED NOVEMBER 2008 ...................................................................................................................................................
www.ti.com
The UCD9240 can control one fan as defined in the PMBus standard. When enabled, the FAN-PWM control
output provides a 156 kHz digital signal, with a duty cycle that is set based on the FAN_COMMAND_1 PMBus
command. The duty cycle can be set from 0% to 100% with 1% resolution.
The FAN-TACH input counts the number of transitions in the tachometer output from the fan in each 1 second
interval. The fan speed may be read by issuing the READ_FAN_SPEED_1 command. The speed is returned in
RPMs.
Different fans may output from one to four tachometer pulses per revolution. The FAN_CONFIG_1_2 command
is used to set the number of tachometer pulses per revolution. The same command is used to indicate whether a
fan is attached.
The UCD9240 can report fan speed faults when the fan speed is too slow for 5 consecutive seconds. The fan
speed fault limit is set by the FAN_SPEED_FAULT_LIMIT command. The status is checked by issuing the
STATUS_FAN_1_2 command. See the UCD92xx PMBUS Command Reference for a complete description of
each command.
Figure 14. Example Fan Control Circuit
The UCD9240 uses Error Correcting Code (ECC) to improve data integrity and provide high reliability storage of
Data Flash contents. ECC uses dedicated hardware to generate extra check bits for the user data as it is written
into the Flash memory. This adds an additional six bits to each 32-bit memory word stored into the Flash array.
These extra check bits, along with the hardware ECC algorithm, allow for any single bit error to be detected and
corrected when the Data Flash is read.
When designing a power supply it is necessary to determine the stability of the closed loop system. The usual
way to do this is to determine the open loop gain versus frequency and from the open loop gain determine the
gain margin and phase margin. Figure 15 shows a block diagram of a complete control loop using the UDC9240.
Each component of the loop gain that is a function of frequency is labeled "Gx". Constant gain components are
labeled "Kx".
CONSTANT GAIN COMPONENTS DESCRIPTION
Transfer function for the power stage circuit consisting of the FET switches, LC output filter
G
plant
and load.
G
div
Transfer function for the VOUT sense divider and its capacitive filter network.
K
AFE
Analog fron-end amplifier gain.
K
EADC
Gain of the 6-bit EADC in units of LSBs/V
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Product Folder Link(s): UCD9240