参数资料
型号: LTC4266AIUHF-4#PBF
厂商: LINEAR TECHNOLOGY CORP
元件分类: 电源管理
英文描述: POWER SUPPLY MANAGEMENT CKT, PQCC38
封装: 7 X 5 MM, LEAD FREE, PLASTIC, MO-220WHKD, QFN-38
文件页数: 16/28页
文件大小: 325K
代理商: LTC4266AIUHF-4#PBF
LTC4266A/LTC4266C
23
4266acf
they are staggered by at least 0.55μs to help reduce volt-
age transients on the main supply. If a port is turned off
via MSD, the corresponding Detection and Classification
Enable bits are cleared, so the port will remain off until
the host explicitly re-enables detection.
SERIAL DIGITAL INTERFACE
Overview
TheLTC4266A/LTC4266Ccommunicateswiththehostus-
ingastandardSMBus/I2C2-wireinterface.TheLTC4266A/
LTC4266C is a slave-only device, and communicates with
the host master using the standard SMBus protocols.
Interrupts are signaled to the host via the INT pin. The
Timing Diagrams (Figures 5 through 9) show typical
communicationwaveformsandtheirtimingrelationships.
More information about the SMBus data protocols can be
found at www.smbus.org.
The LTC4266A/LTC4266C requires both the VDD and VEE
supplyrailstobepresentfortheserialinterfacetofunction.
Bus Addressing
The LTC4266A/LTC4266C’s primary serial bus address is
010xxxxb, with the lower four bits set by the AD3-AD0
pins; this allows up to 16 LTC4266A/LTC4266Cs on a
single bus. All LTC4266A/LTC4266Cs also respond to
the address 0110000b, allowing the host to write the
same command (typically configuration commands) to
multiple LTC4266A/LTC4266Cs in a single transaction. If
the LTC4266A/LTC4266C is asserting the INT pin, it will
also respond to the alert response address (0001100b)
per the SMBus spec.
Interrupts and SMBAlert
Most LTC4266A/LTC4266C port events can be configured
to trigger an interrupt, asserting the INT pin and alerting
the host to the event. This removes the need for the host
to poll the LTC4266A/LTC4266C, minimizing serial bus
trafficandconservinghostCPUcycles.MultipleLTC4266A/
LTC4266Cs can share a common INT line, with the host
using the SMBAlert protocol (ARA) to determine which
LTC4266A/LTC4266C caused an interrupt.
Register Description
For information on serial bus usage and device configura-
tion and status, refer to the LTC4266A/LTC4266C Software
Programming documentation.
EXTERNAL COMPONENT SELECTION
Power Supplies and Bypassing
The LTC4266A/LTC4266C requires two supply voltages to
operate. VDD requires 3.3V (nominally) relative to DGND.
VEE requires a negative voltage of between –44V and –57V
for Type 1 PSEs, –50V to –57V for Type 2 PSEs or –54.75V
to –57V for LTPoE++ PSEs, relative to AGND. The relation-
ship between the two grounds is not fixed; AGND can be
referenced to any level from VDD to DGND, although it
should typically be tied to either VDD or DGND.
VDD provides power for most of the internal LTC4266A/
LTC4266C circuitry, and draws a maximum of 3mA. A
ceramic decoupling cap of at least 0.1μF should be placed
fromVDDtoDGND,ascloseaspracticaltoeachLTC4266A/
LTC4266C chip.
Figure 14 shows a three component low dropout regula-
tor for a negative supply to DGND generated from the
negative VEE supply. VDD is tied to AGND and DGND is
negativereferencedtoAGND.Thisregulatordrivesasingle
LTC4266A/LTC4266C device. In Figure 15, DGND is tied
to AGND in this boost converter circuit for a positive VDD
supply of 3.3V above AGND. This circuit can drive multiple
LTC4266A/LTC4266C devices and opto couplers.
ApplicAtions inForMAtion
Figure 14. Negative LDO to DGND
4266AC F14
R5
750k
D1
CMHZ4687-4.3V
C1
0.1F
Q2
CMPTA92
VEE
VDD
LTC4266
AGND
VEE
AGND
DGND
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