參數(shù)資料
型號(hào)： LTC1703
廠商： Linear Technology Corporation
元件分類： 通用總線功能
英文描述： Synchronous 8-Bit Up/Down Binary Counters 24-PDIP 0 to 70
中文描述： 雙550kHz的同步二相開(kāi)關(guān)穩(wěn)壓控制器5位VID
文件頁(yè)數(shù)： 11/36頁(yè)
文件大?。?/td> 343K
代理商： LTC1703
11
LTC1703
This constant frequency operation brings with it a couple
of benefits. Inductor and capacitor values can be chosen
with a precise operating frequency in mind and the feed-
back loop components can be similarly tightly specified.
Noise generated by the circuit will always be in a known
frequency band with the 550kHz frequency designed to
leave the 455kHz IF band free of interference. Subharmonic
oscillation and slope compensation, common headaches
with constant frequency current mode switchers, are
absent in voltage mode designs like the LTC1703.
During the time that QT is on, its source (the SW pin) is at
V
IN
. V
IN
is also the power supply for the LTC1703. How-
ever, QT requires V
IN
+ V
GS(ON)
at its gate to achieve
minimum R
ON
. This presents a problem for the LTC1703—
it needs to generate a gate drive signal at TG higher than
its highest supply voltage. To accomplish this, the TG
driver runs from floating supplies, with its negative supply
attached to SW and its power supply at BOOST. This
allows
it to slew up and down with the source of QT. In combination
with a simple external charge pump (Figure 2),
this allows
the LTC1703 to completely enhance the gate of QT without
requiring an additional, higher supply voltage.
The two channels of the LTC1703 run from a common
clock, with the phasing chosen to be 180
°
from side 1 to
side 2. This has the effect of doubling the frequency of the
switching pulses seen by the input bypass capacitor,
significantly lowering the RMS current seen by the capaci-
tor and reducing the value required (see the 2-Phase
section).
Feedback Amplifier
Each side of the LTC1703 senses the output voltage at
V
OUT
with an internal feedback op amp (see Block Dia-
gram). This is a real op amp with a low impedance output,
85dB open-loop gain and 25MHz gain-bandwidth product.
The positive input is connected internally to an 800mV
reference, while the negative input is connected to the FB
pin. The output is connected to COMP, which is in turn
connected to the soft-start circuitry and from there to the
PWM generator.
Unlike many regulators that use a resistor divider con-
nected to a high impedance feedback input, the LTC1703
is designed to use an inverting summing amplifier
topology with the FB pin configured as a virtual ground.
This allows flexibility in choosing pole and zero locations
not available with simple g
m
configurations. In particular,
it allows the use of “type 3” compensation, which pro-
vides a phase boost at the LC pole frequency and signifi-
cantly improves loop phase margin (see Figure 3). The
Feedback Loop/Compensation section contains a de-
tailed explanation of type 3 feedback loops. Note that side
1 of the LTC1703 includes R1 and R
B
internally as part
of the VID DAC circuitry.
MIN/MAX COMPARATORS
Two additional feedback loops keep an eye on the primary
feedback amplifier and step in if the feedback node moves
±
5% from its nominal 800mV value. The MAX comparator
(see Block Diagram) activates whenever FB rises more
than 5% above 800mV. It immediately turns the top
MOSFET (QT) off and the bottom MOSFET (QB) on and
keeps them that way until FB falls back within 5% of its
nominal value. This pulls the output down as fast as pos-
sible, preventing damage to the (often expensive) load. If
FB rises because the output is shorted to a higher supply,
QB will stay on until the short goes away, the higher supply
Figure 2. Floating TG Driver Supply
Figure 3. “Type 3” Feedback Loop (Side 2 Shown)
+
TG
BOOST
SW
BG
PGND
PV
CC
D
CP
C
IN
+
C
OUT
1703 F02
V
OUT
L
EXT
V
IN
QT
QB
C
CP
1
μ
F
LTC1703
0.8V
V
OUT
R
B
1703 F03
COMP
–
+
FB
FB
C2
C3
C1
R2
R1
R3
APPLICATIOU
W
U
U
相關(guān)PDF資料
PDF描述
LTC1703CG Synchronous 8-Bit Up/Down Binary Counters 24-PDIP 0 to 70
LTC1704 Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70
LTC1704B Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70
LTC1705 Dual 550kHz Synchronous Switching Regulator Controller with 5-Bit VID and 150mA LDO
LTC1705EGN Dual 550kHz Synchronous Switching Regulator Controller with 5-Bit VID and 150mA LDO
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC1703CG 功能描述:IC REG SW DUAL SYNC VID 28SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件
LTC1703CG#PBF 功能描述:IC REG SW DUAL SYNC VID 28SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:2,000 系列:- 應(yīng)用:控制器，DSP 輸入電壓:4.5 V ~ 25 V 輸出數(shù):2 輸出電壓:最低可調(diào)至 1.2V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:30-TFSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:30-TSSOP 包裝:帶卷 (TR)
LTC1703CG#TR 制造商:Linear Technology 功能描述:LDO Cntrlr REG CTRLR 0.9V to 2V 28-Pin SSOP T/R
LTC1703CG#TRPBF 功能描述:IC REG SW DUAL SYNC VID 28SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件
LTC1703IG 功能描述:IC REG SW DL SYNC W/VID 28-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件
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