TPS2359 Datasheet, PDF (29/51 Pages) Texas Instruments – TPS2359 Full Featured Dual-Slot AdvancedMC™ Controller

TPS2359
www.ti.com ................................................................................................................................................... SLUS792D – FEBRUARY 2008 – REVISED JUNE 2008
APPLICATION INFORMATION
Introduction
The TPS2359 controls two 12-V power paths and two 3.3-V power paths. Each power path can draw from a
single common supply, or from two independent supplies. The TPS2359 occupies a 36-pin QFN package. An I²C
interface not only enables the implementation of two AdvancedMC™ slots using one small integrated circuit, but
it also provides many opportunities for design customization. The following sections describe the main functions
of the TPS2359 and provide guidance for designing systems around this device.
Control Logic and Power-On Reset
The TPS2359's circuitry, including the I²C interface, draws power from an internal bus fed by a preregulator. A
capacitor attached to the VINT pin provides decoupling and output filtering for this preregulator. It can draw
power from any of four inputs (IN12A, IN12B, IN3A, or IN3B) or from any of four outputs (OUT12A, OUT12B,
OUT3A, or OUT3B). This feature allows the internal circuitry to function regardless of which channels receive
power, or from what source. The four external FET drive pins (PASSA, PASSB, BLKA, and BLKB) are held low
during startup to ensure that the two 12-V channels remain off. The internal 3.3-V channels are also held off.
When the voltage on the internal VINT rail exceeds approximately 1 V, the power-on reset circuit loads the
internal registers with the default values listed in Detailed Description of Registers section.
Enable Functions
Table 13 lists the specific conditions required to enable each of the four channels of the TPS2359. The 3.3-V
channels each have an active-high enable pin with a 200-kΩ internal pullup resistor. The enable pin must be
pulled high, or allowed to float high, in order to enable the channel. The I²C interface includes an enable bit for
each of the four channels. The bit corresponding to a channel must be set in order to enable it. All four channels
also include bleed down threshold comparators. Setting the bleed down control bit ensures that a channel cannot
turn on until its output voltage drops below about 100 mV. This feature supports applications in which removal
and restoration of power re-initializes the state of downstream loads. The 12-V channels also include a
cross-connection feature to support PICMG.AMC™ and MicroTCA™ requirements. When enabled, this feature
ensures that when a 3.3-V output drops below 2.85 V the associated 12-V channel will automatically shut off.
This feature can be disabled by setting the DCC bit in Register 6.
Channel
3A
3B
12A
12B
Enable pins
EN3A > 1.4 V
EN3B > 1.4 V
Table 13. Enable Requirements
Enable bits
3AEN = 1
3BEN = 1
12AEN = 1
12BEN = 1
Bleed down
OUT3A < 0.1 V or 3AUV = 0
OUT3B < 0.1 V or 3BUV = 0
OUT12A < 0.1 V or 12AUV = 0
OUT12B < 0.1 V or 12BUV = 0
Cross connection
3APG = 0 or DCC = 1
3BPG = 0 or DCC = 1
Copyright © 2008, Texas Instruments Incorporated
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