an9983

Single Output Mobile-Friendly PWM Controller
®
Application Note
The ISL6224 single PWM controller delivers high efficiency
and tight regulation from a voltage regulating synchronous
buck DC/DC converter. The ISL6224 PWM power supply
controller was designed especially for chip set and memory
bank applications in high performance notebook PCs, subnotebook PCs, and PDAs. The MOSFET drivers, output
voltage monitoring, output current monitoring, and protection
circuitry are included in a single 16 lead SSOP package. The
ISL6224EVAL1 evaluation board reference design provides
an efficient, cost effective and compact power solution.
High efficiency is maintained over a wide load range through
automatic selection of fixed frequency PWM synchronous
rectification mode, also known as continuous conduction
mode (CCM), or hysteretic diode emulation mode (HYS).
The IC enters CCM in response to heavy loads and (HYS)
mode in response to light loads, boosting efficiency. Forced
CCM (FCCM) disables hysteretic mode. Efficiency is further
enhanced by using the converters lower MOSFET RDS(ON)
as a current sense element. Voltage feed-forward duty-cycle
ramp modulation, average current mode control, and internal
feedback compensation provide fast response to input
voltage transients and output load transients.
The ISL6224 features output voltage adjustable in the range
from 0.9V to 5.5V and a selectable switching frequency of
either 300kHz or 600kHz. When operated from battery
voltages ranging from 4V to 24V, a switching frequency of
300kHz is recommended. When operating from 5V, a
switching frequency of 300kHz may be used or, to reduce
the size of the output filter, 600kHz may be used.
Quick Start Evaluation
Circuit Setup
The ISL6224EVAL1 board is designed for easy evaluation
using standard laboratory equipment. Refer to Table 2 for
the range of input and output voltages and currents.
Switch Settings
The ISL6224EVAL1 board is shipped with the four position
dip switch S1 set for 2.5V output. S1 controls the ENABLE
function “EN” and selects the output voltage. Figure 1
illustrates S1 position names and Table 1 describes the
function of each switch position.
February 2003
AN9983.1
EN
Vo #3 (1.25V)
Vo #2 (2.5V)
Vo #1 (3.3V)
FIGURE 1. SWITCH S1 BIT POSITION NAMES
TABLE 1. SWITCH S1 FUNCTIONAL DESCRIPTION
POSITION
STATE
FUNCTION
UP
ENABLES CONVERTER
DOWN
DISABLES CONVERTER
UP
3.3V OUTPUT SELECTED
EN
Vo #1
DOWN
UP
3.3V OUTPUT DESELECTED
2.5V OUTPUT SELECTED
Vo #2
DOWN
UP
2.5V OUTPUT DESELECTED
1.25V OUTPUT SELECTED
Vo #3
DOWN
1.25V OUTPUT DESELECTED
NOTE: If Vo #1, Vo #2 and Vo #3 switches are all down, then the
output voltage of the converter will be equal to Vref, which is 0.9 V.
Only one voltage selection switch is UP at any time.
Jumper Settings
Jumper JP1 enables or inhibits hysteretic mode. If the shunt
jumper is installed across the two pins located on the left, the
IC will be allowed to operate in hysteretic mode, should the
need arise. If the shunt jumper is installed across the two
pins located on the right, the IC will be forced into continuous
conduction mode. The evaluation board comes set for
hysteretic mode.
Jumper JP2 selects the optimum duty cycle ramp gain and
switching frequency. Jumper JP2 has three different
positions each of which will have one side of the shunt
jumper connected to the pin labeled “U3p1”. Refer to Table 2
for the recommended jumper position. The ISL6224EVAL1
board is shipped with JP2 in the “5V 300kHz” position.
JP3 is used to measure the current (ICC) drawn by the VCC
pin from the 5V power supply. When making efficiency
measurements that include VCC, be sure to measure ICC
from JP3. A substantial current is drawn by the red and
green LED and should not be included in determining the
efficiency of the converter.
1
1-888-INTERSIL or 321-724-7143
|
Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2003. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note 9983
TABLE 2. EVALUATION BOARD INPUT/OUTPUT REQUIREMENTS
OPERATION
MODE
INPUT VOLTAGE (V)
OUTPUT VOLTAGE
(V)
MIN OUTPUT
CURRENT (A)
TYPICAL OUTPUT
CURRENT (A)
MAX OUTPUT
CURRENT (A)
VIN 5-24V 300kHz
4 to 24
0.9 to 5.5
0
2
3
VIN 5V 300kHz
5
0.9 to 3.3
0
1
2
VIN 5V 600kHz
5
0.9 to 3.3
0
1
2
Connect the Input Power Supplies
• Connect a 1AMP, 0 to +5VDC Power Supply as follows:
- Before connecting to the evaluation board, turn on the
power supply and adjust the output to +5V then turn off.
- Power Supply positive terminal to the VCC post (J7).
- Power Supply negative terminal to the GND post (J6).
Vout (2V/div)
SOFT Pin (1V/div)
• Connect a 5AMP, 0 to +24VDC Power Supply as follows:
- Before connecting to the evaluation board, turn on the
power supply and adjust the output to +5V then turn off.
- Power Supply positive terminal to the VIN post (J2).
- Power Supply negative terminal to the GND post (J8).
PGOOD Pin (5V/div)
ENABLE Pin (5V/div)
Connect the Output Load
• Connect a 5AMP Electronic Load as follows:
- Electronic Load positive terminal to the VOUT post (J4).
- Electronic Load negative terminal to the GND post (J3).
FIGURE 2. SOFT-START ON 3.3V OUTPUT (2ms/Div)
Output Ripple
Operation
Examine Start-up Waveforms
NOTE: VIN MUST BE TURNED ON BEFORE VCC IN ALL CASES
Turn on the VIN power supply and the VCC power supply.
Move the EN bit of S1 to the UP position. The start up
sequence may be observed by using an oscilloscope. In
Figure 2 the voltage on the SOFT pin of the IC, the output
voltage at TP5, the power good signal at TP3, and the
voltage of the enable signal at post J12 show typical
waveforms. The voltage on the SOFT pin of the IC is
produced by a 5µA current source charging a user supplied
capacitor. The ramp time of the soft start voltage is
controlled by the value of the charging capacitor. The output
voltage follows the soft-start voltage. The green LED will
illuminate when the output is within 10% of the nominal
value. If the EN bit of switch S1 is moved to the DOWN
position the LED will be red, indicating the converter is off.
When a fault condition occurs the LED will be RED even
though the EN bit of S1 is in the UP position. The fault latch
may be cleared by turning the VCC power supply off, then
on again.
2
The ISL6224EVAL1 evaluation board is populated with one
330µF/6.3V SANYO POSCAP output capacitor which has
40mΩ ESR at 100kHz. Figures 3 to 8 show the output
voltage ripple and phase node voltage when the converter is
operating in various modes and various combinations of VIN
and Fs. Please see the ISL6224 data sheet for detailed
instructions on how to select the output capacitor.
Transient Response
The transient response of the converter is the time interval
∆T required to slew the inductor current from an initial value
to a final value such that the output voltage stays
constrained within a specified range. The inductor ripple
current affects the transient response performance. Figures
9 to 14 show the transient performance of the evaluation
board.
NOTE: In following figures; CH1: Vout = 2.5 V, AC coupled.
Application Note 9983
Evaluation Board Performance Graphs
Vin=15 V, Fs=300kHZ
Vin=15 V, Fs= 300kHz
Vripple = 34mV
Vripple = 50mV
Phase Node
Phase Node
FIGURE 3. HYSTERETIC MODE AT ZERO LOAD CURRENT
FIGURE 4. PWM MODE AT FULL LOAD CURRENT
Vin=5 V, Fs=300kHz
Vin=5 V, Fs=300kHz
Vripple = 21mV
Vripple = 28mV
Phase Node
FIGURE 5. HYSTERETIC MODE AT ZERO LOAD CURRENT
3
Phase Node
FIGURE 6. PWM MODE AT FULL LOAD CURRENT
Application Note 9983
Evaluation Board Performance Graphs
(Continued)
Vin=5 V, Fs=600kHz
Vin=5 V, Fs=600kHz
Vripple = 16mV
Vripple = 19mV
Phase Node
Phase Node
FIGURE 7. HYSTERETIC MODE AT ZERO LOAD CURRENT
∆V = 98mV
Vin=15 V, Fs=300kHz
FIGURE 8. PWM MODE AT FULL LOAD CURRENT
Vin=15 V, Fs=300kHz
∆V = 104mV
Vout=2.5V, AC Coupled,
Load Current
Load Current
FIGURE 9. HYSTERETIC MODE TRANSIENT RESPONSE
FIGURE 10. PWM MODE TRANSIENT RESPONSE
4
5
Application Note 9983
Evaluation Board Performance Graphs
(Continued)
∆V = 84mV
Vin=5 V, Fs=300kHz
Vin=5 V, Fs=300kHz
Load Current
Load Current
FIGURE 11. HYSTERETIC MODE TRANSIENT RESPONSE
∆V = 84mV
Vin=5 V, Fs=600kHz
Load Current
FIGURE 13. HYSTERETIC MODE TRANSIENT RESPONSE
5
∆V = 84mV
FIGURE 12. PWM MODE TRANSIENT RESPONSE
Vin=5 V, Fs=600kHz
∆V = 78mV
Load Current
FIGURE 14. PWM MODE TRANSIENT RESPONSE
Application Note 9983
Over Current Protection
Efficiency
The ISL6224 monitors the converter output current by
measuring the voltage developed across the RDS(ON) of the
lower MOSFET and feeding it into the Isense pin through a
scaling resistor. The current detection is used by the
average current mode control loop and by the over current
detection circuit. The scaling resistor is chosen such that it
will flow 75µA of current when the converter is delivering full
load current. It is important to understand that the current
detected by the Isense pin is the sum of the DC AMPS at the
output of the converter and the positive peak of the inductor
ripple current. On page 9 of the ISL6224 data sheet is the
formula to calculate the expected peak to peak inductor
ripple current for a particular combination of VIN, VOUT,
switching frequency, and output choke inductance. The
value of “Iomax” is the sum of one half the calculated peak to
peak inductor ripple current plus the value of the output full
load current of the converter. The value of “Iomax” is now
inserted into the Risen calculation on page 6 of the ISL6224
data sheet. The over current set point Ioc is typically set at
180% of “Iomax”. The value of Ioc and the value of Risen are
inserted into the Rocset calculation on page 6 of the
ISL6224 data sheet. The ISL6224EVAL1 evaluation board
has been adjusted for 3.0 full load amps and approximately
6.3A peak inductor current for over current protection. Figure
15 shows a typical shutdown waveform when the load is
over the limit.
The ISL6224 evaluation was designed to use the lower
MOSFETs RDS(ON) to increase efficiency. Figures 16
through 18 show the efficiency at various output currents
and input voltages.
7.2 V
10.8 V
14.4 V
24 V
Efficiency
98.00%
93.00%
88.00%
83.00%
78.00%
0
0.5
1
1.5
2
2.5
3
3.5
Output Current
FIGURE 16. EFFICIENCY WHEN VOUT = 5V
5V
7.2 V
10.8 V
14.4 V
24 V
98.00%
96.00%
94.00%
Efficiency
Vin=15 V, Fs=300kHz
Vin=5.6 V
92.00%
90.00%
88.00%
86.00%
84.00%
82.00%
80.00%
0
1
1.5
2
2.5
FIGURE 17. EFFICIENCY WHEN VOUT = 3.3V
Phase Node
Efficiency
T0
5.0 V
7.2 V
0.5
1
10.8 V
14.4 V
24 V
100%
98%
96%
94%
92%
90%
88%
86%
84%
82%
80%
78%
0
1.5
2
2.5
Output Current
FIGURE 18. EFFICIENCY WHEN VOUT = 2.5V
6
3
Output Current
Inductor Current
FIGURE 15. OUTPUT OVERLOAD SHUT DOWN
0.5
3
Application Note 9983
Shutdown by Enable
Output Voltage Setpoint Calculation
When the EN bit of S1 is moved to the DOWN position the
PWM stops and the inductor current decays to zero amps
and the output capacitors discharge. A typical shutdown
waveform is shown in Figure 19.
The output voltage of the converter is set by connecting a
two resistor voltage divider across the output. The feedback
voltage divider output is connected to the VSEN pin of the
IC. The voltage at the VSEN pin is 0.9V when the converter
output is in regulation. The voltage at the VSEN pin is
internally compared to a 0.9V reference voltage and passed
on to the next stage of the PWM generation circuits. On the
ISL6224EVAL1 evaluation board the two resistor voltage
divider feedback network consists of R10 (top resistor) and
(R15 or R16 or R17) bottom resistors. Each bottom resistor
chooses a different output voltage. The resistors are
selected by switch S1. The equation for the setpoint of the
output voltage is shown below.
Vin=15 V, Fs=300kHz
,
Vout
R10 × Vref
Ry = -----------------------------Vo – Vref
Inductor Current
Where Ry is bottom resistor, Vo is the required output
voltage and Vref is the reference voltage.
Enable Pin
Some of the most popular output voltage setpoints are
calculated in Table 3.
TABLE 3. OUTPUT VOLTAGE SETPOINT
FIGURE 19. SHUT DOWN BY ENABLE PIN
7
Vo
1.25V
1.5V
2.5V
3.3V
5.0V
R10
11.8K
11.8K
11.8K
11.8K
11.8K
Ry
30.1K
17.8K
6.65K
4.42K
2.59K
5
4
3
2
1
ICC MEASURE
VCC
J7
C4
R19
100K
1%
0805
2
1.0uF
1812
50V
D3
4
1
R4
150K
1%
0805
BAT54WT1
SOT323
C10
C13
L1
D1
C2
C3
C6
C7
C8
C23
C24
L3
D4
1.0uF
1812
50V
10uF
1812
25V
0 OHM
2010
NI
SMB
NI
1812
NI
1812
NI
1812
NI
1812
NI
1812
NI
1812
NI
1812
NI
1812
NI
SMB
8
TP2
ENABLE
J12
GND
J1
C25
R8
71.5K
1%
0805
1.0uF
10V
1206
C21
NI
0603
C12
16
Pgood
Boot
15
3
EN
Ugate
14
4
OCset
Phase
13
Isense
12
5
Vout
6
Vsen
Vcc
11
7
SOFT
Lgate
10
8
GND
Pgnd
9
ISL6224
15nF
10V
1206
GND
PGND
0.0
0805
0.15uF
1206
16V
L-
U2
1
8
2
7
3
6
4
5
TP4
R9
5.1
5%
1206
C22
1.0uF
10V
1206
U1
4
R6
1.30K
1% 0805
J8
56u
OSCON
25V
5
6
7
8
2
FCCM
GND
SO8
PHASE
C
C5
1800pF
50V
0805
FDS6912A
PGND
L2
6.2A
6.4uH
U4
4
SO8
PGND
VOUT
J4
TP5
B
B
R10
11.8K
1%
0805
C18
1.0uF
10V
1206
+
C16
+
C17
NI
NI
D4
D4
GND
C15
330u
6.3V
D4
6TPB330M
+
J3
8
7
6
5
C19
0.1 uF
50V
0805
VOUT
R12
680
5%
0805
1
2
CR1
RED
A
S1
KAL2104ER
LXA3025IGC
3
4
3
PGOOD
TP3
R13
680
5%
0805
1
2
3
4
R11
100K
1%
0805
GREEN
Q1
BSS123LT1
1
2
ENABLE
Vo#3
1.25V
R14
100K
1%
0805
R16
30.1K
1%
0805
Vo#1
3.30V
R17
4.42K
1%
0805
SOT23
A
Building 2A,Suite 105
4020 Stirrup Creek Drive
Durham, NC 27703
Phone: (919) 405 3650
Fax: (919) 405 3651
Title
ISL6224 EVALUATION BOARD
Size
Date:
5
4
PGND
GND
Vo#2
2.50V
R15
6.65K
1%
0805
3
FIGURE 20. ISL6224EVAL1 EVALUATION BOARD SCHEMATIC
2
Document Number
Rev
ISL6224EVAL1
B
Sheet
1
1
of
1
Application Note 9983
C
VIN
C11
D
C1
1
2
3
U3
1
R5
+
5
6
7
8
MODE SELECT
J2
JP2
1
2
3
1
3
ETQP6F6R4HFA
68uF
D Case
16V
Tant
VIN
300KHZ 4V-24V VIN
1
C20
FCCM
L+
3
+
2
300KHZ 5V VIN
D
CCM/HYS
JP1
TP1
600KHZ 5V VIN
GND
J6
2
JP3
3
FCCM
1
Application Note 9983
TABLE 4. BILL OF MATERIALS REV B FOR ASSEMBLY ISL6224EVAL1
ITEM
QTY
UNITS
REFERENCE
DESIGNATOR
1
1
ea
2
1
3
DESCRIPTION
MFG
PART NUMBER
CR1
LED, SMD, 4P, POLARIZED,
RED/GRN
LUMEX
SSL-LXA3025IGC-TR
ea
C1
CAP, OSCON, RADIAL, F-SIZE,
56µF, 25V, 20%
SANYO
25SP56M
1
ea
C13
CAP, X5R, 1812, 10µF, 25V, 20%
TAIYO YUDEN
CE-TMK432BJ106MM
4
2
ea
C4, C10
CAP, X7R, 1812, 1.0µF, 50V, 10%
KEMET
C1812C105K5RAC
5
1
ea
C5
CAP, X7R, 0805, 1800pF, 50V, 10%
KEMET
C0805C182K5RAC
6
1
ea
C11
CAP, X7R, 1206, 0.15µF, 16V, 10%
KEMET
C1206C154K4RAC
7
1
ea
C12
CAP, X7R, 1206, 0.015µF, 10V, 10%
KEMET
C1206C153K8RAC
8
3
ea
C18, C22, C25
CAP, X7R, 1206, 1.0µF, 10V, 10%
KEMET
C1206C105K8RAC
9
1
ea
C19
CAP, X7R, 0805, 0.1µF, 50V, 10%
KEMET
C0805C104K5RAC
10
1
ea
C20
CAP, TANT, D-CASE, 68µF, 16V,
20%
KEMET
T494D686M016AS
11
1
ea
C15
CAP, POSCAP, D4-CASE, 330µF,
6.3V, 20%
SANYO
6TPB330M
12
1
ea
D3
DIODE, SCHOTTKY BARRIER,
SOT323, 30V, 200mA
ON SEMICONDUCTOR
BAT54WT1
13
1
ea
Q1
TRANSISTOR, MOSFET, NCHANNEL, SOT23, 100V, 170mA
ON SEMICONDUCTOR
BSS123LT1
14
1
ea
U3
IC, PWM CONTROLLER, 24V,
16PIN, SSOP
INTERSIL
ISL6224CA
15
1
ea
U2
TRANSISTOR, MOSFET, NCHANNEL, DUAL, LOGIC LEVEL,
30V, 6.0A
FAIRCHILD
FDS6912A
16
1
ea
L1
RESISTOR, Cu ALUMINA, 2010, 3.0
mΩ MAX, 30.0A
IRC
LRC-LRZ-2010-R000
17
1
ea
L2
INDUCTOR, PWR, SMD, 5.7mm,
6.4uH, 6.2A,
PANASONIC
ETQP6F6R4H
18
1
ea
R5
RESISTOR, TF, 0805, 0Ω, 125mW,
5%
PANASONIC
ERJ6GEY0R00V
19
1
ea
R4
RESISTOR, TF, 0805, 150K, 1/10W,
1.0%
PANASONIC
ERJ6ENF1503V
20
1
ea
R9
RESISTOR, TF, 1206, 5.1Ω, 250mW,
5%
PANASONIC
ERJ8GEYJ5R1V
21
1
ea
R10
RESISTOR, TF, 0805, 11.8K,
100mW, 1.0%
PANASONIC
ERJ6ENF1182V
22
3
ea
R11, R14, R19
RESISTOR, TF, 0805, 100K,
100mW, 1.0%
PANASONIC
ERJ6ENF1003V
23
2
ea
R12, R13
RESISTOR, TF, 0805, 680Ω,
125mW, 5%
PANASONIC
ERJ6GEYJ681V
24
1
ea
R15
RESISTOR, TF, 0805, 6.65K,
100mW, 1.0%
PANASONIC
ERJ6ENF6651V
25
1
ea
R16
RESISTOR, TF, 0805, 30.1K,
100mW, 1.0%
PANASONIC
ERJ6ENF3012V
26
1
ea
R17
RESISTOR, TF, 0805, 4.42K,
100mW, 1.0%
PANASONIC
ERJ6ENF4421V
9
Application Note 9983
TABLE 4. BILL OF MATERIALS REV B FOR ASSEMBLY ISL6224EVAL1 (Continued)
ITEM
QTY
UNITS
REFERENCE
DESIGNATOR
27
1
ea
28
1
29
DESCRIPTION
MFG
PART NUMBER
R6
RESISTOR, TF, 0805, 1.30K,
100mW, 1.0%
PANASONIC
ERJ6ENF1301V
ea
R8
RESISTOR, TF, 0805, 71.50K,
100mW, 1.0%
PANASONIC
ERJ6ENF7152V
3
ea
TP1, TP2, TP3
TEST POINT, THRU HOLE, LOOP,
WHITE
KEYSTONE
5002
30
2
ea
TP4, TP5
TEST POINT, THRU HOLE, SCOPE
PROBE, COMPACT
TEKTRONICS
131-5031-00
31
8
ea
J1, J2, J3, J4, J6, J7,
J8, J12
TERMINAL POST, THRU HOLE
KEYSTONE
1502-2
32
2
ea
JP1, JP2
HEADER, 1x3, THRU HOLE,
2.54mm PITCH
BERG/FCI
68000-236-1X3
33
1
ea
JP3
HEADER, 1x2, THRU HOLE,
2.54mm PITCH
BERG/FCI
68000-236-1X2
34
3
ea
JP1, JP2, JP3
SHUNT, TWO PIN, 2.54mm PITCH
SULLINS
SPC02SYAN
35
1
ea
S1
SWITCH, FOUR POSITION, SM
E-SWITCH
KAL2104R
C2, C3, C6, C7, C8,
C16, C17, C21, C23,
C24, D1, D4, L3, U1,
U4
NO INSTALL
36
10
Application Note 9983
Silk Screens
FIGURE 21. TOP LAYER
FIGURE 22. SILK SCREEN TOP
FIGURE 23. BOTTOM LAYER
FIGURE 24. SILK SCREEN BOTTOM
11
Application Note 9983
Silk Screens
(Continued)
FIGURE 25. GROUND INTERNAL
FIGURE 26. POWER INTERNAL
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
12
Similar pages