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PDF ISL8104 Data sheet ( Hoja de datos )
| Número de pieza | ISL8104 | |
| Descripción | Synchronous Buck Pulse-Width Modulator (PWM) Controller | |
| Fabricantes | Intersil Corporation | |
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Data Sheet
February 13, 2006
ISL8104
FN9257.0
Synchronous Buck Pulse-Width
Modulator (PWM) Controller
The ISL8104 is a high performance synchronous controller
for demanding DC/DC converter applications. It provides
overcurrent fault protection and is designed to safely start-up
into prebiased output loads.
The output voltage of the converter can be precisely
regulated to as low as 0.597V, with a maximum tolerance of
±1% over the commercial temperature range, and ±1.5%
over the industrial temperature range.
The ISL8104 provides simple, single feedback loop, voltage-
mode control with fast transient response. It includes a
triangle-wave oscillator that is adjustable from below 50kHz
to over 1.5MHz. Full (0% to 100%) PWM duty cycle support
is provided.
The error amplifier features a 15MHz gain-bandwidth
product and 6V/µs slew rate which enables high converter
bandwidth for fast transient performance.
The ISL8104's overcurrent protection monitors the current
by using the rDS(ON) of the upper MOSFET which eliminates
the need for a current sensing resistor.
Pinouts
ISL8104
(14 LD NARROW SOIC AND 16 LD QFN)
TOP VIEW
RT 1
OCSET 2
SS 3
COMP 4
FB 5
EN 6
GND 7
14 VCC
13 PVCC
12 LGATE
11 PGND
10 BOOT
9 UGATE
8 PHASE
16 15 14 13
SS 1
COMP 2
FB 3
EN 4
12 PVCC
11 LGATE
10 PGND
9 BOOT
5678
Features
• Operates from an +8V ±5% to +14V ±10% Input
• Excellent Output Voltage Regulation
- 0.597V Internal Reference
- ±1% Over the Commercial Temperature Range
- ±1.5% Over the Industrial Temperature Range
• Simple Single-Loop Control Design
- Voltage-Mode PWM Control
• Fast Transient Response
- High-Bandwidth Error Amplifier
- Full 0% to 100% Duty Ratio
- Leading and Falling Edge Modulation
• Small Converter Size
- Constant Frequency Operation
- Oscillator Programmable from 50kHz to Over 1.5MHz
• 14V High Speed MOSFET Gate Drivers
- 2.0A Source/3A Sink at 14V Low Side Gate Drive
- 1.25A Source/2A Sink at 14V High Side Gate Drive
- Drives Two N-Channel MOSFETs
• Overcurrent Fault Monitor
- High-Side MOSFET’s rDS(ON) Sensing
- Reduced ~120ns Blanking Time
• Converter can Source and Sink Current
• Soft-Start Done and an External Reference Pin for
Tracking Applications are Available in the QFN Package
• Pin Compatible with ISL6522 and ISL6535
• Supports Start-Up into Prebiased Loads
• Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
• Test & Measurement Instruments
• Routers Switches
• Medical Instrumentation
• Industrial Applications
• Telecom/Datacom Applications
Ordering Information
PART #
(Note)
PART
TEMP.
PACKAGE PKG.
MARKING RANGE (°C) (Pb-free) DWG. #
ISL8104CBZ 8104CBZ
0 to 70 14 Ld SOIC
M14.15
ISL8104IBZ 8104IBZ
-40 to 85 14 Ld SOIC
M14.15
ISL8104CRZ 8104CRZ 0 to 70 16 Ld 4x4 QFN L16.4x4
ISL8104IRZ 8104IRZ -40 to 85 16 Ld 4x4 QFN L16.4x4
Add “-T” suffix for tape and reel.
NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets;
molding compounds/die attach materials and 100% matte tin plate termination finish,
which are RoHS compliant and compatible with both SnPb and Pb-free soldering
operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow
temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J
STD-020.
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
1 page  
ISL8104
Electrical Specifications Recommended Operating Conditions, unless otherwise noted specifications in bold are valid for process,
temperature, and line operating conditions. (Continued)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN TYP MAX UNITS
REFERENCE
Reference Voltage
System Accuracy
REFIN Current Source (QFN Only)
TJ = 0°C to 70°C
TJ = -40°C to 85°C
TJ = 0°C to 70°C
TJ = -40°C to 85°C
0.591
0.588
-1.0
-1.5
-4
0.597
0.597
-
-
-6
0.603
0.606
1.0
1.5
-8
V
V
%
%
µA
REFIN Threshold (QFN Only)
2.10 - 3.50
V
REFIN Offset (QFN Only)
-3 -
3 mV
GATE DRIVERS
Upper Drive Source Current
Upper Drive Source Impedance
Upper Drive Sink Current
Upper Drive Sink Impedance
Lower Drive Source Current
Lower Drive Source Impedance
Lower Drive Sink Current
Lower Drive Sink Impedance
SSDONE (QFN ONLY)
IU_SOURCE VBOOT - VPHASE = 14V, 3nF Load - GBD
RU_SOURCE 90mA Source Current
IU_SINK VBOOT - VPHASE = 14V, 3nF Load - GBD
RU_SINK 90mA Source Current
IL_SOURCE VPVCC = 14V, 3nF Load - GBD
RL_SOURCE 90mA Source Current
IL_SINK VPVCC = 14V, 3nF Load - GBD
RL_SINK 90mA Source Current
- 1.25 -
- 2.0 -
-2-
- 1.3 -
-2-
- 1.3 -
-3-
- 0.94 -
A
Ω
A
Ω
A
Ω
A
Ω
SSDONE Low Output Voltage
ISSDONE = 2mA
0.30 V
Typical Performance Curves
1000
RRT PULLUP
TO +14V
100
RRT PULLDOWN
TO GND
10
10 100
SWITCHING FREQUENCY (kHz)
FIGURE 1. RRT RESISTANCE vs FREQUENCY
1000
Functional Pin Description (SOIC/QFN)
RT (Pin 1/14)
This pin provides oscillator switching frequency adjustment.
By placing a resistor (RRT) from this pin to GND, the
switching frequency is set from between 200kHz and
1.5MHz according to the following equation:
RRT[kΩ] ≈ -F---s----[--k---H-----z----]6---5–---0--2--0-0---0----[---k---H-----z----] – 1.3kΩ
(RRT to GND)
80
70
60
CGATE = 3300pF
50
CGATE = 1000pF
40
30
20
10 CGATE = 10pF
0
100 200 300 400 500 600 700 800 900 1000
SWITCHING FREQUENCY (kHz)
FIGURE 2. BIAS SUPPLY CURRENT vs FREQUENCY
Alternately ISL8104’s switching frequency can be lowered
from 200kHz to 50kHz by connecting the RT pin with a
resistor to VCC according to the following equation:
RRT[kΩ] ≈ 2----0---0----[--k----H---5--z-5--]--0--–-0---F0----s---[---k---H-----z----] + 70kΩ
(RRT to VCC)
5 FN9257.0
February 13, 2006
5 Page 
ISL8104
components. Consult with the manufacturer of the load on
specific decoupling requirements.
Use only specialized low-ESR capacitors intended for
switching-regulator applications for the bulk capacitors.
The bulk capacitor’s ESR will determine the output ripple
voltage and the initial voltage drop after a high slew-rate
transient. An aluminum electrolytic capacitor's ESR value is
related to the case size with lower ESR available in larger
case sizes. However, the equivalent series inductance
(ESL) of these capacitors increases with case size and can
reduce the usefulness of the capacitor to high slew-rate
transient loading. Unfortunately, ESL is not a specified
parameter. Work with your capacitor supplier and measure
the capacitor’s impedance with frequency to select a
suitable component. In most cases, multiple electrolytic
capacitors of small case size perform better than a single
large case capacitor.
Output Inductor Selection
The output inductor is selected to meet the output voltage
ripple requirements and minimize the converter’s response
time to the load transient. The inductor value determines the
converter’s ripple current and the ripple voltage is a function
of the ripple current. The ripple voltage and current are
approximated by the following equations:
∆I
=
V-----I--N-----------V----O----U-----T-
Fs x L
•
V-----O----U----T--
VIN
∆VOUT= ∆I x ESR
Increasing the value of inductance reduces the ripple current
and voltage. However, the large inductance values reduce
the converter’s response time to a load transient.
One of the parameters limiting the converter’s response to a
load transient is the time required to change the inductor
current. Given a sufficiently fast control loop design, the
ISL8104 will provide either 0% or 100% duty cycle in
response to a load transient. The response time is the time
required to slew the inductor current from an initial current
value to the transient current level. During this interval the
difference between the inductor current and the transient
current level must be supplied by the output capacitor.
Minimizing the response time can minimize the output
capacitance required.
The response time to a transient is different for the
application of load and the removal of load. The following
equations give the approximate response time interval for
application and removal of a transient load:
TRISE = -VL---O-I--N---×--–---I-V-T---R-O---A-U---N-T--
TFALL
=
L----O------×----I--T----R----A----N--
VOUT
where: ITRAN is the transient load current step, TRISE is the
response time to the application of load, and TFALL is the
response time to the removal of load. With a +5V input
source, the worst case response time can be either at the
application or removal of load and dependent upon the
output voltage setting. Be sure to check both of these
equations at the minimum and maximum output levels for
the worst case response time.
Input Capacitor Selection
Use a mix of input bypass capacitors to control the voltage
overshoot across the MOSFETs. Use small ceramic
capacitors for high frequency decoupling and bulk capacitors
to supply the current needed each time Q1 turns on. Place
the small ceramic capacitors physically close to the
MOSFETs and between the drain of Q1 and the source of
Q2.
The important parameters for the bulk input capacitor are the
voltage rating and the RMS current rating. For reliable
operation, select a bulk capacitor with voltage and current
ratings above the maximum input voltage and largest RMS
current required by the circuit. The capacitor voltage rating
should be at least 1.25 times greater than the maximum
input voltage, a voltage rating of 1.5 times greater is a
conservative guideline. The RMS current rating requirement
for the input capacitor of a buck regulator is approximately
1/2 the DC load current.
For a through hole design, several electrolytic capacitors
(Panasonic HFQ series or Nichicon PL series or Sanyo
MV-GX or equivalent) may be needed. For surface mount
designs, solid tantalum capacitors can be used, but caution
must be exercised with regard to the capacitor surge current
rating. These capacitors must be capable of handling the
surge-current at power-up. The TPS series available from
AVX, and the 593D series from Sprague are both surge
current tested.
MOSFET Selection/Considerations
The ISL8104 requires at least 2 N-Channel power
MOSFETs. These should be selected based upon rDS(ON),
gate supply requirements, and thermal management
requirements.
In high-current applications, the MOSFET power dissipation,
package selection and heatsink are the dominant design
factors. The power dissipation includes two loss
components; conduction loss and switching loss. At a
300kHz switching frequency, the conduction losses are the
largest component of power dissipation for both the upper
and the lower MOSFETs. These losses are distributed
between the two MOSFETs according to duty factor (see the
following equations). Only the upper MOSFET exhibits
switching losses, since the schottky rectifier clamps the
switching node before the synchronous rectifier turns on.
These equations assume linear voltage-current transitions
and do not adequately model power loss due the reverse-
recovery of the lower MOSFETs body diode. The
gate-charge losses are dissipated by the ISL8104 and don't
heat the MOSFETs. However, large gate-charge increases
11 FN9257.0
February 13, 2006
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet ISL8104.PDF ] | |
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