DATASHEET
ISL85033
Wide V
IN
Dual Standard Buck Regulator With 3A/3A Continuous Output Current
The ISL85033 is a dual standard buck regulator capable of 3A
per channel continuous output current. With an input range of
4.5V to 28V, it provides a high frequency power solution for a
variety of point of load applications.
The PWM controller in the ISL85033 drives an internal
switching N-Channel power MOSFET and requires an external
Schottky diode to generate the output voltage. The integrated
power switch is optimized for excellent thermal performance
up to 3A of output current. The PWM regulator switches at a
default frequency of 500kHz and it can be user programmed
or synchronized from 300kHz to 2MHz. The ISL85033 utilizes
peak current mode control to provide flexibility in component
selection and minimize solution size. The protection features
include overcurrent, UVLO and thermal overload protection.
The ISL85033 is available in a small 4mmx4mm Thin Quad
Flat No-Lead (TQFN) Pb-free package.
FN6676
Rev 8.00
February 17, 2015
Features
• Wide input voltage range from 4.5V to 28V
• Adjustable output voltage with continuous output current up
to 3A
• Current mode control
• Adjustable switching frequency from 300kHz to 2MHz
• Independent power-good detection
• Selectable in-phase or out-of-phase PWM operation
• Independent, sequential, ratiometric or absolute tracking
between outputs
• Internal 2ms soft-start time
• Overcurrent/short circuit protection, thermal overload
protection, UVLO
• Boot undervoltage detection
• Pb-free (RoHS compliant)
Related Literature
•
AN1574
“ISL85033DUALEVAL1Z Wide VIN Dual Standard
Buck Regulator With 3A/3A Output Current”
•
AN1585
“ISL85033EVAL2Z (Small Form) Wide VIN Dual
Standard Buck Regulator With 3A/3A Output Current - Short
Form”
•
AN1584
“ISL85033EVAL2Z (Small Form) Wide VIN Dual
Standard Buck Regulator With 3A/3A Output Current - Long
Form”
•
AN1605
“ISL85033CRSHEVAL1Z Wide VIN Current sharing
Standard Buck Regulator With 6A Output Current”
Applications
• General purpose point-of-load DC/DC power conversion
• Set-top boxes
• FPGA power and STB power
• DVD and HDD drives
• LCD panels, TV power
• Cable modems
100
90
EFFICIENCY (%)
80
70
60
50
40
0.0
12V
OUT
1MHz
0.5
1.0
1.5
2.0
2.5
3.0
OUTPUT LOAD (A)
FIGURE 1. EFFICIENCY vs LOAD, V
IN
= 28V, T
A
= +25°C
FN6676 Rev 8.00
February 17, 2015
Page 1 of 26
ISL85033
Table of Contents
Pin Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Typical Application Schematics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Thermal Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Recommended Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Typical Performance Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Operation Initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power-on Reset and Undervoltage Lockout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Enable and Disable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power-good. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Voltage Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Protection Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buck Regulator Overcurrent Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Overload Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
BOOT Undervoltage Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Application Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Synchronization Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Inductor Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buck Regulator Output Capacitor Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Current Sharing Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input Capacitor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loop Compensation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Theory of Compensation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PWM Comparator Gain Fm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Stage Transfer Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rectifier Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Derating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Layout Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
16
16
16
16
17
17
18
18
18
18
18
18
18
19
19
19
20
20
20
21
22
22
Output Tracking and Sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
About Intersil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Package Outline Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
FN6676 Rev 8.00
February 17, 2015
Page 2 of 26
ISL85033
Pin Configuration
ISL85033
(28 LD TQFN)
TOP VIEW
SYNCOUT
23
PGOOD1
PGOOD2
22
SYNCIN
24
28
27
26
COMP1
FB1
SS1
PGND1
BOOT1
PHASE1
PHASE1
1
2
3
4
5
6
7
PD
SGND
25
NC
FS
21 COMP2
20 FB2
19 SS2
18 PGND2
17 BOOT2
16 PHASE2
15 PHASE2
8
VIN1
9
VIN1
10
EN1
11
VCC
12
EN2
13
VIN2
14
VIN2
Pin Descriptions
PIN NUMBER
1, 21
2, 20
SYMBOL
COMP1, COMP2
FB1, FB2
PIN DESCRIPTION
COMP1, COMP2 are the output of the error amplifier.
Feedback pin for the regulator. FB is the negative input to the voltage loop error amplifier. COMP is the
output of the error amplifier. The output voltage is set by an external resistor divider connected to FB.
In addition, the PWM regulator’s power-good and undervoltage protection circuits use FB1, FB2 to monitor
the regulator output voltage.
Soft-start pins for each controller. The SS1, SS2 pins control the soft-start and sequence of their respective
outputs. A single capacitor from the SS pin to ground determines the output ramp rate. See the
“Output
Tracking and Sequencing” on page 16
for soft-start and output tracking/sequencing details. If SS pins are
tied to VCC, an internal soft-start of 2ms will be used. Maximum C
SS
value is 100nF.
Power ground connections. Connect directly to the system GND plane.
Floating bootstrap supply pin for the power MOSFET gate driver. The bootstrap capacitor provides the
necessary charge to turn on the internal N-Channel MOSFET. Connect an external capacitor from this pin to
PHASE.
Switch node output. It connects the source of the internal power MOSFET with the external output inductor
and with the cathode of the external diode.
The input supply for the power stage of the PWM regulator and the source for the internal linear regulator
that provides bias for the IC. Place a minimum of 10µF ceramic capacitance from each VIN to GND and
close to the IC for decoupling.
PWM controller’s enable inputs. The PWM controllers are held off when the pin is pulled to ground. When
the voltage on this pin rises above 2V, the PWM controller is enabled. If EN1, EN2 pins are driven by an
external signal, the minimum off-time for EN1, EN2 should be:
EN_T_off
s
=
10s
C
SS
2.2nF
where C
SS
is the soft-start pin capacitor (nF). The ISL85033 does not have debouncing to EN1, EN2 external
signals.
Output of the internal 5V linear regulator. Decouple to PGND with a minimum of 4.7µF ceramic capacitor.
This pin is provided only for internal bias of ISL85033 (not to be loaded with current over 10mA).
3, 19
SS1, SS2
4, 18
5, 17
PGND1, PGND2
BOOT1, BOOT2
6, 7, 15, 16
8, 9, 13, 14
PHASE1, PHASE2
VIN1, VIN2
10, 12
EN1, EN2
11
VCC
FN6676 Rev 8.00
February 17, 2015
Page 3 of 26
ISL85033
Pin Descriptions
(Continued)
PIN NUMBER
23
24
SYMBOL
SYNCOUT
SYNCIN
PIN DESCRIPTION
Synchronization output. Provides a signal that is the inverse of the SYNCIN signal.
Connect to an external signal for synchronization from 300kHz to 2MHz (negative edge trigger). SYNCIN is
not allowed to be floating.
When SYNCIN = logic 0, PHASE1 and PHASE2 are running at 180° out-of-phase.
When SYNCIN = logic 1, PHASE1 and PHASE2 are running at 0° in-phase.
When SYNCIN = an external clock, PHASE1 and PHASE2 are running at 180° out-of-phase.
External SYNC frequency applied to the SYNCIN pin should be at least 2.4 x the internal switching frequency
setting.
Signal ground connections. The exposed pad must be connected to SGND and soldered to the PCB. All
voltage levels are measured with respect to this pin.
This is a no connection pin.
Frequency selection pin. Tie to VCC for 500kHz switching frequency. Connect a resistor to GND for
adjustable frequency from 300kHz to 2MHz.
Open-drain power-good output that is pulled to ground when the output voltage is below regulation limits or
during the soft-start interval. There is an internal 5MΩ internal pull-up resistor.
The exposed pad must be connected to the system GND plane with as many vias as possible for proper
electrical and thermal performance.
25
26
27
22, 28
SGND
NC
FS
PGOOD2, PGOOD1
PD
FN6676 Rev 8.00
February 17, 2015
Page 4 of 26
ISL85033
Typical Application Schematics
V
OUT2
R
5
25.5k
C
4
68pF
COMP2
FB2
R
6
8.06k
C
5
470pF
R
8
69.8k
21
R
2
8.06k
C
2
470pF
FB1
R
4
69.8k
1
COMP1
R
1
42.2k
C
1
68pF
V
OUT1
20
VCC
VCC
VCC
FS 27
SS2 19
SS1 3
PGOOD2
V
OUT2
3A
C
13
47µF
L
2
7µH
PGOOD1
PHASE2
15/16
D
2
B340B
C
12
10nF
BOOT2 17
24
SYNCIN
22
28
2
8/9 VIN1
13/14
VIN2
10µF
C
72
L1
7µH
C
8
10nF
V
OUT1
3A
C
71
20µF
ISL85033
6/7
PHASE1
5 BOOT1
23 4/18
SYNCOUT
EN2
PGND1/2
12
26
NC
10 25
SGND
VCC
EN1
11
4.7µF
C
9
47µF
D
1
B340B
FIGURE 2. DUAL 3A OUTPUT (V
IN
RANGE FROM 4.5V TO 28V)
V
OUT1
R
5
42.2k
C
4
68pF
R
7
0
FB2
FB2
R
6
8.06k
C
5
1nF
COMP2
COMP1
R
8
34k
21
COMP2
FB2
FB1
1
2
8/9
13/14
VIN1
VIN2
10µF
PHASE1
C8
10nF
L
1
7µH
D
1
B340B
C
9
47µF
C72
V
OUT1
6A
C
71
20µF
6/7
20
VCC
C
ss2
47nF
FS
SS2
SS1
C
ss1
47nF
27
19
3
PGOOD2 22
PGOOD1 28
PHASE2
15/16
ISL85033
V
OUT1
C
13
47µF
L
2
7µH
D
2
B340B
C
12
10nF
BOOT2
17
24
SYNCIN
23 4/18
PGND1/2
EN2
SYNCOUT
12
26
NC
10
EN1
25
SGND
VCC
11
4.7µF
5
BOOT1
FIGURE 3. SINGLE 6A OUTPUT (V
IN
RANGE FROM 4.5V TO 28V) CURRENT SHARING
FN6676 Rev 8.00
February 17, 2015
Page 5 of 26
Microcontroller MCU
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