数据搜索系统，热门电子元器件搜索
  Chinese  ▼
ALLDATASHEETCN.COM

X  

预览 PDF HTML

ADP1850ACPZ-R7 数据表(PDF) 17 Page - Analog Devices

部件名 ADP1850ACPZ-R7
功能描述  Wide Range Input, Dual/Two-Phase, DC-to-DC Synchronous Buck Controller
PDF  32 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
制造商  AD [Analog Devices]
网页  http://www.analog.com
标志 AD - Analog Devices

ADP1850ACPZ-R7 数据表(HTML) 17 Page - Analog Devices

Back Button ADP1850ACPZ-R7 Datasheet HTML 13Page - Analog Devices ADP1850ACPZ-R7 Datasheet HTML 14Page - Analog Devices ADP1850ACPZ-R7 Datasheet HTML 15Page - Analog Devices ADP1850ACPZ-R7 Datasheet HTML 16Page - Analog Devices ADP1850ACPZ-R7 Datasheet HTML 17Page - Analog Devices ADP1850ACPZ-R7 Datasheet HTML 18Page - Analog Devices ADP1850ACPZ-R7 Datasheet HTML 19Page - Analog Devices ADP1850ACPZ-R7 Datasheet HTML 20Page - Analog Devices ADP1850ACPZ-R7 Datasheet HTML 21Page - Analog Devices Next Button
Zoom Inzoom in Zoom Outzoom out
 17 / 32 page
background image
Data Sheet
ADP1850
Rev. C | Page 17 of 32
ACCURATE CURRENT-LIMIT SENSING
RDSON of the MOSFET can vary by more than 50% over the
temperature range. Accurate current limit sensing is achieved
by adding a current sense resistor from the source of the low-
side MOSFET to PGNDx. Make sure that the power rating of the
current sense resistor is adequate for the application. Apply the
previous equation and calculate RILIM by replacing RDSON_MAX
with RSENSE. Figure 30 illustrates the implementation of accurate
current limit sensing.
VIN
ADP1850
DHx
SWx
ILIMx
DLx
RILIM
RSENSE
Figure 30. Accurate Current Limit Sensing
SETTING THE SLOPE COMPENSATION
In a current-mode control topology, slope compensation is
needed to prevent subharmonic oscillations in the inductor
current and to maintain a stable output. The external slope
compensation is implemented by summing the amplified sense
signal and a scaled voltage at the RAMPx pin. To implement the
slope compensation, connect a resistor between RAMPx and
the input voltage. The resistor, RRAMP, is calculated by
MAX
DSON
CS
RAMP
R
A
L
R
_
9
10
7
×
×
=
where:
7 × 109 is an internal parameter.
L is the inductance (with units in H) of the inductor.
RDSON_MAX is the low-side MOSFET maximum on resistance.
ACS is the gain, either 3 V/V, 6 V/V, 12 V/V, or 24 V/V, of the
current sense amplifier (see the Setting the Current Sense Gain
section for more details).
RDSON is temperature dependent and can vary as much as
0.4%/oC. Choose RDSON at the maximum operating temperature.
The voltage at RAMPx is fixed at 0.2 V, and the current going
into RAMPx should be between 10 µA and 160 µA. Make sure
that the following condition is satisfied:
A
160
V
2
.
0
A
10
µ
≤
−
≤
µ
RAMP
IN
R
V
For instance, with an input voltage of 12 V, RRAMP should not
exceed 1.1 MΩ. If the calculated RRAMP produces less than 10 µA,
then select an RRAMP value that produces between 10 µA and 15 µA.
Figure 31 illustrates the connection of the slope compensation
resistor, RRAMP, and the current sense gain resistor, RCSG.
VIN
ADP1850
DHx
SWx
ILIMx
DLx
RILIM
RCSG
RAMP
RRAMP
Figure 31. Slope Compensation and CS Gain Connection
SETTING THE CURRENT SENSE GAIN
The voltage drop across the external low-side MOSFET is
sensed by a current sense amplifier by multiplying the peak
inductor current and the RDSON of the MOSFET. The result is
then amplified by a gain factor of either 3 V/V, 6 V/V, 12 V/V,
or 24 V/V, which is programmable by an external resistor, RCSG,
connected to the DLx pin. This gain is sensed only during
power-up and not during normal operation. The amplified
voltage is summed with the slope compensation ramp voltage
and fed into the PWM controller for a stable regulation voltage.
The voltage range of the internal node, VCS, is between 0.4 V
and 2.2 V. Select the current sense gain such that the internal
minimum amplified voltage (VCSMIN) is above 0.4 V and the
maximum amplified voltage (VCSMAX) is 2.1 V. Note that VCSMIN
or VCSMAX is not the same as VCOMP, which has a range of 0.85 V
to 2.25 V. Make sure that the maximum VCOMP (VCOMPMAX) does
not exceed 2.2 V to account for temperature and part-to-part
variations. See the following equations for VCSMIN, VCSMAX, and
VCOMPMAX:
CS
MIN
DSON
LPP
CSMIN
A
R
I
V
×
×
−
=
_
2
1
V
75
.
0
CS
MAX
DSON
LPP
LOADMAX
CSMAX
A
R
I
I
V
V
×
×
−
+
=
_
)
2
1
(
75
.
0
CSMAX
RAMP
ON
IN
COMPMAX
V
R
t
V
V
+
×
−
=
pF
100
)
V
2
.
0
(
where:
VCSMIN is the minimum amplified voltage of the internal current
sense amplifier at zero output current.
VCSMAX is the maximum amplified voltage of the internal current
sense amplifier at maximum output current.
RDSON_MIN is the low-side MOSFET minimum on resistance. The
zero-current level voltage of the current sense amplifier is 0.75 V.
ILPP is the peak-to-peak ripple current in the inductor.
ILOADMAX is the maximum output dc load current.
VCOMPMAX is the maximum voltage at the COMP pin.
100 pF is an internal parameter.
tON is the high-side driver (DH) on time.



Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32


数据表 下载

Go To PDF Page


链接网址



ALLDATASHEET是否为您带来帮助?  [ DONATE ] 

关于 Alldatasheet   |   广告服务   |   联系我们   |   隐私政策   |   数据表链接    |   链接交换   |   制造商名单
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com