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PDF XR79106 Data sheet ( Hoja de datos )
| Número de pieza | XR79106 | |
| Descripción | 6A Synchronous Step-Down COT Power Module | |
| Fabricantes | Exar | |
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XR79106
22V, 6A Synchronous Step-Down
COT Power Module
Description
The XR79106 is part of a family of 22V synchronous step-down
power modules combining the controller, drivers, inductor, passive
components and MOSFETs in a single package for point-of-load
supplies. This module requires very few external components leading
to ease of design and fast time to market. The XR79106 has load
current rating of 6A. A wide 4.5V to 22V input voltage range allows
for single supply operation from industry standard 5V, 12V and
19.6V rails.
With a proprietary emulated current mode Constant On-Time (COT)
control scheme, the XR79106 provides extremely fast line and load
transient response using ceramic output capacitors. It requires no
loop compensation, simplifying circuit implementation and reducing
overall component count. The control loop also provides 0.2% load
and 0.2% line regulation and maintains constant operating frequency.
A selectable power saving mode, allows the user to operate in
Discontinuous Current Mode (DCM) at light current loads significantly
increasing the converter efficiency.
A host of protection features, including overcurrent, over temperature,
short-circuit and UVLO, helps achieve safe operation under abnormal
operating conditions.
The XR79106 is available in a RoHS-compliant, green/halogen-free
space-saving 8mm x 8mm x 4mm QFN package.
Typical Application
FEATURES
■■ 6A step-down power module
4.5V to 22V wide single input voltage
≥0.6V adjustable output voltage
■■ Controller, drivers, inductor, passive
components and MOSFETs integrated in
one package
■■ Proprietary constant on-time control
No loop compensation required
Stable with ceramic output capacitors
Programmable 100ns to1µs on-time
Constant 600kHz to 800kHz frequency
Selectable CCM or DCM/CCM
operation
■■ Precision enable and power-good flag
■■ Programmable soft-start
■■ 8mm x 8mm x 4mm QFN package
APPLICATIONS
■■ FPGA, DSP and processor supplies
■■ Distributed power architecture
■■ Point-of-load converters
■■ Power supply modules
■■ Base stations
■■ Switches and routers
■■ Servers
VIN
ENABLE/MODE
POWER GOOD
CIN RPGOOD
CVCC CSS
RON
VIN PVIN
EN/MODE
PGOOD
VOUT
VCC XR79106
SW
SS ILIM
TON
AGND
PGND
FB
RLIM
Figure 1. Typical Application
VOUT
RFB1
RFB2
COUT
100
800kHz
95
90
85
80 600kHz
5.0V
75
3.3V
2.5V
1.8V
70
1.5V
1.2V
1.0V
65
0123456
IOUT (A)
Figure 2. Efficiency, 12VIN
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1 page  
Pin Configuration
XR79106
SS 1
PGOOD 2
FB 3
AGND 4
AGND 5
VIN 6
VCC 7
PGND 8
SW 9
SW 10
SW 11
SW 12
PGND 13
AGND
PAD
BST
PAD
SW
PAD
PGND PAD
41 PGND
PVIN
PAD 40 PGND
39 PGND
38 VOUT
37 VOUT
36 VOUT
35 VOUT
VOUT
PAD
34 VOUT
33 VOUT
32 VOUT
31 VOUT
30 VOUT
29 VOUT
Pin Functions
Pin Number
1
2
3
4, 5, 53, 54,
AGND Pad
6
7
8
13-19, 39-43,
PGND Pad
9-12, 20-23,
SW Pad
24-38,
VOUT Pad
45-49,
PVIN Pad
50, 51,
BST Pad
52
55
56
Pin Name
SS
PGOOD
FB
AGND
VIN
VCC
PGND
PGND
SW
VOUT
PVIN
BST
ILIM
EN/MODE
TON
Type Description
A
OD, O
A
Soft-start pin. Connect an external capacitor between SS and AGND to program the soft-start rate based
on the 10μA internal source current.
Power-good output. This open-drain output is pulled low when VOUT is outside the regulation.
Feedback input to feedback comparator. Connect with a set of resistors to VOUT and AGND in order to
program VOUT.
A Analog ground. Control circuitry of the IC is referenced to this pin. Connect to PGND.
PWR
PWR
PWR
IC supply input. Provides power to internal LDO. Connect to PVIN pins.
The output of LDO. Bypass with a 4.7μF capacitor to AGND.
Controller low-side driver ground. Connect with a short trace to closest PGND pins or PGND pad.
PWR Ground of the power stage. Should be connected to the system’s power ground plane.
PWR
Switching node. It internally connects the source of the high-side FET, the drain of the low-side FET,
the inductor and bootstrap capacitor. Use thermal vias and/or sufficient PCB land area in order to heatsink
the low-side FET and the inductor.
PWR Output of the power stage. Place the output filter capacitors as close as possible to these pins.
PWR Power stage input voltage. Place the input filter capacitors as close as possible to these pins.
A
Controller high-side driver supply pin. It is internally connected to SW via a 0.1μF bootstrap capacitor.
Leave these pins floating.
A Overcurrent protection programming. Connect with a short trace to SW pins.
I
Precision enable pin. Pulling this pin above 1.9V will turn the IC on and it will operate in forced CCM. If the
voltage is raised above 3.0V, then the IC will operate in DCM or CCM depending on load.
A Constant on-time programming pin. Connect with a resistor to AGND.
NOTE:
A = Analog, I = Input, O = Output, OD = Open Drain, PWR = Power.
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5 Page 
XR79106
Applications Information
Functional Description
XR79106 is a synchronous step-down proprietary
emulated current-mode Constant On-Time (COT) module.
The on-time, which is programmed via RON,
is inversely proportional to VIN and maintains a nearly
constant frequency. The emulated current-mode control is
stable with ceramic output capacitors.
Each switching cycle begins with GH signal turning on
the high-side (switching) FET for a preprogrammed time.
At the end of the on-time, the high-side FET is turned off and
the low-side (synchronous) FET is turned on for a preset
minimum time (250ns nominal). This parameter is termed
minimum off-time. After the minimum off-time, the voltage
at the feedback pin FB is compared to an internal voltage
ramp at the feedback comparator. When VFB drops below
the ramp voltage, the high-side FET is turned on and the
cycle repeats. This voltage ramp constitutes an
emulated current ramp and makes possible the use of
ceramic capacitors, in addition to other capacitor types,
for output filtering.
Enable/Mode Input (EN/MODE)
EN/MODE pin accepts a tri-level signal that is used to control
turn on/off. It also selects between two modes of operation:
forced CCM and DCM/CCM. If EN is pulled below 1.8V,
the module shuts down. A voltage between 2.0V and 2.8V
selects the forced CCM mode which will run the module in
continuous conduction at all times. A voltage higher than
3.1V selects the DCM/CCM mode which will run the module
in discontinuous conduction at light loads.
Selecting the Forced CCM Mode
In order to set the module to operate in forced CCM, a voltage
between 2.0V and 2.8V must be applied to EN/MODE.
This can be achieved with an external control signal that
meets the above voltage requirement. Where an external
control is not available, the EN/MODE can be derived
from VIN. If VIN is well regulated, use a resistor divider and
set the voltage to 2.5V. If VIN varies over a wide range,
the circuit shown in Figure 25 can be used to generate
the required voltage. Note that at VIN of 4.5V and 22V
the nominal Zener voltage is 3.8V and 4.7V respectively.
Therefore for VIN in the range of 4.5V to 22V, the circuit
shown in Figure 25 will generate VEN required for
forced CCM.
Selecting the DCM/CCM Mode
In order to set the module operation to DCM/CCM, a voltage
between 3.1V and 5.5V must be applied to EN/MODE pin.
If an external control signal is available, it can be directly
connected to EN/MODE. In applications where an external
control is not available, EN/MODE input can be derived
from VIN. If VIN is well regulated, use a resistor divider
and set the voltage to 4V. If VIN varies over a wide range,
the circuit shown in Figure 26 can be used to generate the
required voltage for DCM/CCM operation.
VIN
RZ
10k
Zener
MMSZ4685T1G or
Equivalent
R1
24.3k, 1%
R2 EN/MODE
35.7k, 1%
Forced CCM, wide VIN range
Figure 25. Selecting Forced CCM by
Deriving EN/MODE from VIN
VIN
Zener
MMSZ4685T1G or
Equivalent
RZ
10k
VEN
EN/MODE
DCM/CCM, wide VIN range
Figure 26. Selecting DCM/CCM by
Deriving EN/MODE from VIN
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11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet XR79106.PDF ] | |
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