参数资料
型号: PT8139N
厂商: TEXAS INSTRUMENTS INC
元件分类: 稳压器
英文描述: 30 A SWITCHING REGULATOR, 400 kHz SWITCHING FREQ-MAX, MSMA31
文件页数: 7/9页
文件大小: 194K
代理商: PT8139N
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
Pin-Coded Output Voltage Programming of the
30-A Rated PT8120 Series Regulators
The PT8120 series of Excalibur ISRs incorporate a
pin-coded output voltage control. These regulators must
be programmed to a specific output voltage from a pre-
set range defined by the regulator model. Programming
is achieved by selectively connecting the control inputs,
“VID0–VID4” (pins 1–5), to the “VID Common” (pin 11). 1
The programming code and voltage range for each model
is defined in the data sheet. Refer to the PT8120 Series
data sheet for more information. The program codes for
the PT8121, PT8122, and PT8124 models are also com-
patible with some of the “Voltage ID” codes defined by
Intel’s VRM specifications. Figure 1 shows the pin-strap
connections for selecting the desired output voltage from
the program code range.
Notes:
1. The programming convention is as follows:-
Logic 0:
Connect to pin 11 (VID Common).
Logic 1:
Open circuit/open drain (See notes 2, & 4)
2. Do not connect pull-up resistors to the voltage
programming pins.
3. To minimize output voltage error, use pin 11 (VID
Common) as the logic “0” reference. If the regulator is
used to power a VRM compatible microprocessor this
may not be practical. In this case connect pin 11 to pins
17–22, or the ground plane close to the regulator.
Figure 1
4. If active devices are used to ground the voltage control
pins, low-level open drain MOSFETs should be used over
bipolar transistors. The inherent Vce(sat) in bipolar devices
introduces errors in the device’s internal voltage control
circuit. Discrete transistors such as the BSS138, 2N7002,
IRLML2402, are examples of appropriate devices.
Active Voltage Programming:
Special precautions should be taken when making changes
to the voltage control progam code while the output is
active. It is recommended that the ISR be powered down
or held placed in standby. Changes made to the program
code while Vout is active induces high current transients
through the device. This is the result of the electrolytic
output capacitors being either charged or discharged to the
new output voltage set-point. The transient current can be
minimized by making only incremental changes to the
binary code, i.e. one LSB at a time. A minimum of 100s
settling time between each program state is also recom-
mended. Making non-incremental changes to VID3 and
VID4 with the output enabled is discouraged. The tran-
sients induced may activate the module’s over-current
protection. If the program code cannot be asserted prior
to power-up, pull pin 6, STBY*, to GND during the
period that the input voltage is applied. The release of
pin 6 will then to allow the device to initiate a soft-start
power-up to the program voltage.
PT8120 Series & PT8139
L
O
A
D
C
OUT
+
C
IN
+
V
IN
V
O =3.3V
GND
V
O SENSE
L
in
1H
GND
PT8121
43
21
31
23–30
617–22
12–16
5
11
VID4 – VID0
Sense
V
IN
V
OUT
STBY
GND
VID
Common
VID0
VID1
VID2
VID3
VID4
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