Datasheet
PMBUS_ADDR0
PMBUS_ADDR1
VDD
To 12-bit ADC
10uA
Ibias
UCD90124A
On/Off Control
Resistors to set
PMBus address
UCD90124A
SLVSAN8 –JANUARY 2012
www.ti.com
Table 10. PMBus Address Assignment Rules (continued)
Address STATUS Reason
11 Avoid Causes conflicts with other devices during program flash updates.
12 Prohibited PMBus alert response protocol
13-125 Available
126 For JTAG Use Default value; may cause conflicts with other devices.
127 Prohibited Used by TI manufacturing for device tests.
Figure 32. PMBus Address-Detection Method
CAUTION
Leaving the address in default state as 126 (0x7E) will enable the JTAG and not allow
using the JTAG compatible pins (36-39) as GPIOs.
DEVICE RESET
The UCD90124A has an integrated power-on reset (POR) circuit which monitors the supply voltage. At power up,
the POR detects the V
33D
rise. When V
33D
is greater than V
RESET
, the device comes out of reset.
The device can be forced into the reset state by an external circuit connected to the RESET pin. A logic-low
voltage on this pin for longer than t
RESET
holds the device in reset. It comes out of reset within 1 ms after RESET
is released and can return to a logic-high level. To avoid an erroneous trigger caused by noise, a pullup resistor
to 3.3 V is recommended.
Any time the device comes out of reset, it begins an initialization routine which lasts approximately 20 ms. During
the initialization routine, the FPWM pins are held low, and all other GPIO and GPI pins are open-circuit. At the
end of the initialization routine, the device begins normal operation as defined by the device configuration.
DEVICE CONFIGURATION AND PROGRAMMING
From the factory, the device contains the sequencing and monitoring firmware. It is also configured so that all
GPOs are high-impedance (except for FPWM/GPIO pins 17-24, which are driven low), with no sequencing or
fault-response operation. See Configuration Programming of UCD Devices, available from the Documentation &
Help Center that can be selected from the Fusion GUI Help menu, for full UCD90124A configuration details.
After the user has designed a configuration file using Fusion GUI, there are three general device-configuration
programming options:
1. Devices can be programmed in-circuit by a host microcontroller using PMBus commands over I
2
C (see the
UCD90xxx Sequencer and System Health Controller PMBus Command Reference).
Each parameter write replaces the data in the associated memory (RAM) location. After all the required
configuration data has been sent to the device, it is transferred to the associated nonvolatile memory (data
flash) by issuing a special command, STORE_DEFAULT_ALL. This method is how the Fusion GUI normally
reads and writes a device configuration.
2. The Fusion GUI (Figure 33) can create a PMBus or I
2
C command script file that can be used by the I
2
C
master to configure the device.
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