IFX80471
Table of Contents
Table of Contents
1
2
3
3.1
3.2
4
4.1
4.2
4.3
5
5.1
5.2
6
6.1
6.2
6.3
7
7.1
7.2
7.3
7.3.1
7.4
7.5
7.6
7.7
7.8
7.8.1
7.8.2
7.8.3
7.8.4
7.8.5
7.8.6
7.8.7
7.8.8
7.8.9
7.9
7.10
8
9
Overview
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Block Diagram
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin Configuration
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Pin Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Pin Definitions and Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
General Product Characteristics
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
7
8
9
Electrical Characteristics
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Typical Performance Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Detailed Circuit Description
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PFM/PWM Step-down regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Battery voltage sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Undervoltage Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Application Information
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output voltage at adjustable version - feedback divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SI_Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Battery sense comparator - voltage divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Undervoltage reset - delay time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
100% duty-cycle operation and dropout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SYNC Input and Frequency Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shutdown Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buck converter circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buck inductance (L1) selection in terms of ripple current: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Determining the current limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PFM and PWM thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buck output capacitor (COUT) selection: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input capacitor (CIN1) selection: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Freewheeling diode / catch diode (D1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buck driver supply capacitor (CBDS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input pi-filter components for reduced EME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Frequency compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Components recommendation - Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Layout recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19
19
20
20
21
21
21
21
22
22
22
23
23
23
23
24
24
24
25
25
25
25
25
26
26
Package Outlines
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Revision History
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Data Sheet
2
Rev. 1.0, 2011-02-07
Step-Down DC/DC Controller
IFX80471
1
Features
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1)
2)
Overview
Input voltage range from 5V up to 60V
Output voltage: 5V fixed or adjustable
Output voltage accuracy: 3%
Output current up to 2.3A
100% maximum duty cycle
Less than 120µA quiescent current at low loads
1)
2µA max. shutdown current at device off (IFX80471SKV)
Fixed 360kHz switching frequency
Frequency synchronization input for external clocks
Current Mode control scheme
Integrated output undervoltage reset circuit
2)
On chip low battery detector (on chip comparator)
Temperature range -40°C to 125 °C
Green Product (RoHS compliant)
dependent on external component
for the adjustable version IFX80471SKV the reset functionality is available for output voltages > 7V
PG-DSO-14
For automotive and transportation applications, please refer to the Infineon TLE and TLF voltage regulator series.
Description
The IFX80471 step-down DC-DC switching controllers provide high efficiency over loads ranging from 1mA up to
2.3A. A unique PWM/PFM control scheme operates with a duty cycle up to 100% resulting in a very low dropout
voltage. This control scheme eliminates minimum load requirements and reduces the supply current under light
loads to 120µA, depending on dimensioning of external components. In addition the adjustable version
IFX80471SKV can be shut down via the Enable input reducing the input current to <2µA. The IFX80471 step-down
controllers drive an external P-channel MOSFET, allowing design flexibility for applications up to 11.5W of output
power at 5V output voltage. The IFX80471 offers high switching frequency of up to 360kHz as well as operation
in continuous-conduction mode and allows the usage of tiny surface-mount inductors. Output capacitor
requirements are also reduced, minimizing PC board area and system costs. The output voltage of the
IFX80471SKV50 is preset to 5V and is adjustable for the IFX80471SKV. The IFX80471SKV50 features a reset
function with a threshold between 4.5V and 4.8V, including a small hysteresis of typ. 50mV. Input voltages of both
IFX80471 versions can be up to 60V.
Type
IFX80471SKV
IFX80471SKV50
Data Sheet
Package
PG-DSO-14
PG-DSO-14
3
Marking
I80471V
I80471V50
Rev. 1.0, 2011-02-07
IFX80471
Pin Configuration
3
3.1
Pin Configuration
Pin Assignment
ENABLE /
SI_ENABLE
FB
VOUT
GND
SYNC
SI_GND
SI
1
2
3
4
5
6
7
14
CS
13
VS
12
GDRV
11
BDS
10
RO
9
8
SO
COMP
Figure 2
Pin Configuration
3.2
Pin
1
Pin Definitions and Functions
Symbol
ENABLE
Function
Active-High enable input (only adjustable version, IFX80471SKV) for the
device.
The device is shut down when ENABLE is driven low. In this shut down-mode the
reference, the output and the external MOSFET are turned off. Connect to logic high
for normal operation.
Active-High enable input (only 5V version, IFX80471SKV50) for SI_GND input.
SI_GND is switched to high impedance when SI_ENABLE is low. High level at
SI_ENABLE connects SI_GND to GND with low impedance. SO is undefined when
SI_ENABLE is low.
Feedback input.
1. For adjustable version (IFX80471SKV) connect this pin to an external voltage
divider from the output to GND (see
Chapter 7.2).
2. For the 5V fixed output voltage version (IFX80471SKV50) the FB is connected to
an on-chip voltage divider supplied internally by VOUT. It does not have to be
connected externally to the output.
Buck output voltage input.
Input for the internal supply. Connect always to the output of the buck converter
(output capacitor).
5
Rev. 1.0, 2011-02-07
1
SI_ENABLE
2
FB
3
VOUT
Data Sheet
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