Datasheet

Input Voltage and Current Monitoring
Temperature Monitoring
CD74HC4051
Temp-rail1A
Temp-rail1B
Temp-rail2A
Temp-rail2B
Temp-rail3A
Temp-rail4A
13
14
15
12
1
5
2
4
+3.3V
Com
S2
S1
S0
-EN
A0
A1
A2
A3
A4
A5
A6
A7
Temp
TMUX2
TMUX1
TMUX0
3
9
10
11
6
16
8
UCD9240
www.ti.com ................................................................................................................................................... SLUS766C – JULY 2008 – REVISED NOVEMBER 2008
The Vin/Iin pin on the UCD9240 monitors the input voltage and current. To measure both input voltage and input
current, an external multiplexer is required. If measurement of only the input voltage, and not input current, is
desired, then a multiplexer is not needed, see Figure 3 . The multiplexer is switched between voltage and current
using the TMUX-0 signal. (This signal is the LSB of the temperature mux select signals, so the TMUX-0 signal is
connected both to the temperature multiplexer as well as the voltage/current multiplexer). The Vin/Iin pin is
monitored using the internal 12-bit ADC and so has a dynamic range of 0 to 2.5V. The fault thresholds for the
input voltage are set using the VIN_OV_FAULT_LIMIT and VIN_UV_FAULT_LIMIT commands. The scaling for
Vin is set using the VIN_SCALE_MONITOR command, and the scaling for Iin is set using the
IIN_SCALE_MONITOR command.
Both the internal device temperature and up to eight external temperatures are monitored by the UCD9240. The
controller supports multiple PMBus commands related to temperature, including READ_TEMPERATURE_1,
which reads the internal temperature, READ_TEMPERATURE_2, which reads the external power stage
temperatures, OT_FAULT_LIMIT, which sets the over temperature fault limit, and OT_FAULT_RESPONSE,
which defines the action to take when the configured limit is exceeded.
If more than one external temperature is to be measured, the UCD9240 provides analog multiplexer select pins
(TMUX0-2) to allow up to 8 external temperatures to be measured. The output of the multiplexer is routed to the
Temp pin. The controller cycles through each of the power stage temperature measurement signals. The signal
from the external temperature sensor is expected to be a linear voltage proportional to temperature. The PMBus
commands TEMPERATURE_CAL_GAIN and TEMPERATURE_CAL_OFFSET are used to scale the measured
temperature-dependent voltage to ° C.
The inputs to the multiplexer are mapped in the order that the outputs are assigned in the PHASE_INFO PMBus
command. For example, if only one power stage is wired to each DPWM, the four temperature signals should be
wired to the first four multiplexer input.
The UCD9240 monitors temperature using the 12-bit monitor ADC, sampling each temperature in turn with a 800
ms sample period. These measurements are smoothed by a digital filter, similar to that used to smooth the
output current measurements. The filter has a time constant 15.5 times the sample interval, or 12.4 s (15.5 × 800
ms = 12.4 seconds). This filtering reduces the probability of false fault detections.
Figure 12. Temperature Mux (4-rail, 6-phase Example)
Below is an example of a system with 2 output voltage rails, where each output is driven by 3 power stages. The
first output voltage rail is driven with PWM-1A, PWM -1B, and PWM-3A. The second output voltage rail is driven
with PWM-2A, PWM-2B, and PWM-4A. The order in which the temperature multiplexer inputs are assigned are
shown in Table 5
Table 5. Temperature Sensor Mapping
TEMPERATURE MUX INPUT POWER STAGE RAIL
A0 PWM-1A Rail-1A
A1 PWM-1B Rail-1B
A2 PWM-3A Rail-1C
A3 PWM-2A Rail-2A
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Product Folder Link(s): UCD9240