SMH4046 Datasheet, PDF (2/51 Pages) List of Unclassifed Manufacturers – Hot-Swap, Active DC Output Control (ADOCTM) Power Manager with I2C lnterface

VCC12 ( +6V to +14V)
5.0V
3.3V
2.0V
1.8V
1.5V
SMH4046
Preliminary Information
RESET
t_DPONA
t_DPONB
t_DPONC
t_DPOND
t_DPONE
t_DPONF
--- _tPTO---
Figure 2 – Example Power Supply Cascade Sequencing and System Initialization Using the SMH4046
GENERAL DESCRIPTION
The SMH4046 is a fully integrated hot swap controller
intended for use on add-in cards that are hot swapped
from powered-on host platforms. The SMH4046
performs a variety of tasks starting with the validation
of proper card insertion and the presence of “in-spec”
voltages at the host platform interface.
Once the SMH4046 switches power on, it continues to
monitor the back-end power to the add-in card and the
host power supply. When programmed to do so, the
SMH4046 immediately asserts the RESET outputs
and powers-down the add-in card when the 12V, 5V or
3.3V supplies drop below a programmable UV or
above an OV threshold.
In addition to the power control for the add-in card, the
SMH4046 provides status signals that can be
employed by the host for the control of bus interface
components.
On-chip EEPROM memory can be used to store serial
ID numbers or other pertinent information for the
individual card or as general-purpose memory. The
FPGA configuration-interface provides a direct
interface for simplified access to the add-in card’s
FPGAs using the I²C interface.
The SMH4046 has the ability to monitor and sequence
up to six power supplies (Figure 1). The SMH4046 can
monitor the 12V input and the internal and external
temperature sensors. The SMH4046 has four
operating modes: Power-on sequencing mode,
monitor and control mode using Active DC Output
Control (ADOC), supply margining mode using ADOC,
and Power-off sequencing mode.
Power-on sequencing can be initiated via the
HST_PWR pin or through the serial interface. In this
mode, the SMH4046 sequences the power supply
channels on in any order by activating the PUPx,
VGATE and DRVREN# outputs while monitoring the
respective converter and host voltages to ensure
correct cascading of the supplies. Cascade-
sequencing is the ability to hold off the next
sequenced supply until the previous supply reaches a
programmed threshold voltage (See Figure 2). A
programmable sequence termination timer can be set
to disable all channels if the power-on sequence stalls.
During this mode, the HEALTHY# output remains
inactive and the RESET output remains active. When
the HEALTHY# output is true and RESET is false, that
signals the end of power-on sequencing mode.
Once the Power-on sequencing mode is complete, the
SMH4046 enters monitor control mode. Once all
supplies have sequenced on and the voltages are
above the UV settings, the Active DC Output Control
(ADOC), if enabled, brings the three DC-DC converter
supply output voltages to their programmed nominal
settings and adjusts the output voltage under all load
conditions. This feature is especially useful for
supplies without sense lines as the monitor VMx pins
can be routed and sense variations at the load. Typical
converters have ±2 to ±5% accuracy output voltage
ratings. The Active DC Output Control feature of the
SMH4046 increases the accuracy to ±0.5%.
Summit Microelectronics, Inc
2082 1.7 08/23/04
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