Si3500
5 0 V I
NPU T
D C
Features
Integrated switching regulator
controller with on-chip power FET
Input range 42 to 57 V
Output can be set from 1.8 to
12 V
Output power up to 10 W
Highly-integrated IC enables
compact solution footprints
TO
DC C
ONVERTER
Supports non-isolated and
isolated switching topologies
Comprehensive protection
circuitry
Transient
external components
Integrated transient surge
suppressor
Integrated dual current-limited
hotswap switch
Integrated switching power FET
Minimal
Applications
VPOSS
16
Description
20
19
18
17
15
The Si3500 is a highly-integrated, high-voltage (42 to 57 V) input dc-to-dc
converter with integrated PWM control and power FET. The output can be
adjusted for various applications in the range of 1.8 to 12 VDC.
The integrated hot swap switch provides a 2-level current limit for slow
charging of the input filter capacitor followed by overcurrent protection at
400 mA.
The hot swap switch overcurrent protection fully protects the Si3500 from
short-circuit damage as long as the inductor does not saturate. For
situations where it is desirable to use a smaller inductor, it is possible to
reduce the overcurrent protection with the addition of one low-cost
transistor.
EROUT
1
2
VSSA
14 NC
13 NC
12 VPOSF
11 NC
10
NC
VSS2
SSFT
VDD
3
4
VNEG
(PAD)
ISOSSFT
5
6
RBIAS
7
HSO
VSS1
8
NC
SWO
FB
3.3 V power supply generation
Internet appliances
for Power over Ethernet Power
Network devices
Sourcing supply, such as Si3452
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50% duty cycle limiting
Low-profile, 5x5 mm, 20-pin QFN
RoHS-compliant
NC
overvoltage protection
Undervoltage lockout
Thermal shutdown protection
Short circuit protection
Ordering Information:
See Ordering Guide on page
page 14.
Pin Assignments
5 x 5 mm QFN
(Top View)
9
VNEG
The Si3500 can be configured to provide an isolated output voltage or a
non-isolated output that is positive or negative with respect to the positive
input rail.
Input undervoltage and overvoltage lockout functions are fully-integrated.
A 65 V input clamp is also integrated. Output voltage softstart is enabled
by just one capacitor to control the output rise time at startup.
Rev. 1.2 1/15
Copyright © 2015 by Silicon Laboratories
Si3500
Si3500
Functional Block Diagram
ISOSSFT
EROUT
Error
Amplifier
VPOS1
VPOS2
RBIAS
SSFT
VDD
FB
SWO
PWM
VNEG
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Si3500
HSO
VSSA
Protection
Central
Bias
Soft
Start
Control
VSS1
VSS2
2
Rev. 1.2
Si3500
T
ABLE
Section
OF
C
ONTENTS
Page
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Rev. 1.2
1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2. Typical Application Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
3. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
3.1. Input Surge Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
3.2. Under Voltage Lockout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
3.3. Dual Current Limit Hot Swap switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
3.4. Switching Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
3.5. Switcher Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
3.6. Switching Regulator Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
4. Layout Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Package Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Recommended PCB Landing Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
3
Si3500
1. Electrical Specifications
Table 1. Recommended Operating Conditions
Description
VPOS – VNEG input voltage
Ambient Operating Temperature
Symbol
VIN
T
A
Min
42
–40
Typ
—
25
Max
57
85
Units
V
°C
Note:
Unless otherwise noted, all voltages referenced to VNEG. All minimum and maximum specifications are guaranteed
and apply across the recommended operating conditions. Typical values apply at nominal supply voltage and ambient
temperature unless otherwise noted.
Table 2. Absolute Maximum Ratings (DC)
1
Type
Voltage
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Description
Rating
VPOS
HSO
VSS1 or VSS2
SWO
2
VPOS
3
VDD
0 to 2
SWO
0 to 3
VSS1, VSS2, or VSSA
Storage
Operating
Rev. 1.2
Unit
V
V
V
V
mA
mA
A
mA
°C
°C
–0.3 to 60
–0.3 to 60
–0.3 to 60
–0.3 to 60
0 to 400
Current
0 to 400
Ambient
Temperature
–65 to 150
–40 to 85
Notes:
1.
Unless otherwise noted, all voltages referenced to VNEG. Permanent device damage may occur if the maximum
ratings are exceeded. Functional operation should be restricted to those conditions specified in the operational
sections of this data sheet. Exposure to absolute maximum rating conditions for extended periods may adversely affect
device reliability.
2.
Averaged over the switching cycle.
3.
VPOS is equal to VPOS1 and VPOS2 tied together for test condition purposes.
4
Si3500
Table 3. Absolute Maximum Ratings (Transient)
1
Type
Voltage
VPOS
2
HSO
VSS1, VSS2, or VSSA
SWO
Current
VPOS
2
Description
Rating
–0.7 to 80
–0.7 to 80
–0.7 to 80
–0.7 to 80
–5 to 5
Unit
V
V
V
V
A
Table 4. Surge Immunity Ratings
1,2
Type
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Description
Contact discharge (IEC 61000-4-2)
JEDEC (JESD22-C101C)
JEDEC (JESD22-A114E)
JEDEC (JESD22-A115A)
Rev. 1.2
Notes:
1.
Unless otherwise noted, all voltages referenced to VNEG. Permanent device damage may occur if the maximum ratings
are exceeded. Functional operation should be restricted to those conditions specified in the operational sections of this
data sheet. Exposure to absolute maximum rating conditions for extended periods may adversely affect device
reliability.
2.
VPOS is equal to VPOS1 and VPOS2 tied together for test condition purposes.
Rating
Unit
kV
kV
V
kV
V
ESD (System-Level) Air discharge (IEC 61000-4-2)
–16.5 to 16.5
–8 to 8
ESD (CDM)
ESD (HBM)
ESD (MM)
–750 to 750
–2 to 2
–150 to 150
Notes:
1.
Permanent device damage may occur if the maximum ratings are exceeded. Functional operation should be restricted
to those conditions specified in the operational sections of this data sheet. Exposure to absolute maximum rating
conditions for extended periods may adversely affect device reliability.
2.
Care should be taken to follow layout guidelines.
5
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