Si85xx
Si85
X X U N I D I R E C T I O N A L
AC
C U R R E N T S E N S O R S
Features
Single-chip ac current
sensor/conditioner
Low loss: Less than 1.3 mΩ
primary series resistance;
less than 2 nH primary
inductance at 25 ºC
Leading-edge noise suppression
eliminates need for leading-edge
blanking
"Ping-Pong" output version
allows one Si85xx to replace two
current transformers in full-bridge
applications
5, 10, and 20 A full-scale versions
FAULT output helps safeguard
operation
1,000 VDC isolation
Accurate to ±5% of measurement
Large 2 V
PP
output pins signal at
full scale
High-side or low-side current
sensing
–40 to 125 ºC operating range
(Si85x4/5/6)
Small 4 x 4 x 1 mm package
Low cost
Pin Assignments:
See page 20
12-Pin QFN
VDD2
R1
R2
GND2
GND3
OUT
NC
IOUT
1
VDD1
IIN
Si850x
TRST
Applications
Power supplies
Motor controls
Lighting equipment
Industrial equipment
R1
R2
1
MODE
Description
The Si85xx products are unidirectional ac current sensors available in full-
scale ranges of 5, 10, and 20 A. Si85xx products are ideal upgrades for
older current-sensing technologies offering size, performance and cost
advantages over current transformers, Hall effect devices, DCR circuits
and other approaches. The Si85xx are extremely low loss, adding less
than 1.3 mΩ of series resistance and less than 2 nH series inductance in
the sensing path at 25 ºC. Current-sensing terminals are isolated from the
other package pins to a maximum voltage of 1,000 VDC.
VDD
GND1
IIN
R3
R4
OUT1
OUT2
Si851x
IOUT
Functional Block Diagram
Patents pending
IIN
R1
R2
R3
R4
Si851x
RESET LOGIC
MODE LOGIC
MODE
R2
VDD
VIN
VDD1
TRST
IIN
GND1
Si850x
IOUT
OUT
GND2
OUT1
METAL SLUG
INTEGRATOR
SIGNAL CONDITIONING
OUT2
R1
PH1
Q1
L
C
PH2
Q2
VOUT
TEMP
SENSOR
ADC
AUTO CALIBRATION
LOGIC
Typical Application
IOUT
GND
VDD
TRST/FAULT
Preliminary Rev. 0.1 7/07
Copyright © 2007 by Silicon Laboratories
TRST/FAULT
GND
Si85xx
This information applies to a product under development. Its characteristics and specifications are subject to change without notice.
Silicon Laboratories Confidential. Information contained herein is covered under non-disclosure agreement (NDA).
Si85xx
2
Preliminary Rev. 0.1
Si85xx
T
A B L E O F
C
O N T E N TS
Section
Page
1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2. Functional Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.1. Under Voltage Lockout (UVLO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
2.2. Device Start-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
2.3. Integrator Reset and Current Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
2.4. Effect of Operating Frequency on Output Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . .8
2.5. Effect of Temperature on Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
2.6. Leading Edge Noise Suppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
2.7. FAULT Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3. Application Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1. Board Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
3.2. Device Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
3.3. Single-Phase Buck Converter Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.4. Full-Bridge Converter Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.5. Push-Pull Converter Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
4. Pin Descriptions—Si85xx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6. Package Outline—12-Pin QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Preliminary Rev. 0.1
3
Si85xx
1. Electrical Specifications
Table 1. Electrical Specifications
TA = –40 to +85 ºC (typical specified at 25 ºC), VDD = 2.7 to 5.5 V
Parameter
Supply Voltage (V
DD
)
Supply Current
Undervoltage Lockout (V
UVLO
)
Undervoltage Lockout Hysteresis
(V
HYST
)
Logic Input HIGH Level
Logic Input LOW Level
Reset Time (t
R
)
R1, R2, R3, R4 Input Rise Time (t
RR
)
R1, R2, R3, R4 Input Fall Time (t
FR
)
Measurement Watchdog Timeout (t
WD
)
Series Input Resistance
Series Inductance
Input/Output Delay
Start-Up Self-Cal Delay (t
CAL
)
Input Common Mode Voltage Range
Operating Input Frequency Range (f)
DC Power Supply Rejection Ratio
Sensitivity
Conditions
Min
2.7
Typ
—
4
2.3
100
—
—
—
—
—
50
1.3
2
50
150
—
—
80
400
200
100
10
50
Max
5.5
7
2.5
—
—
0.8
—
30
30
80
—
—
100
200
1,000
1,200
—
—
—
—
—
—
30
Unit
V
mA
V
mV
V
V
ns
ns
ns
µs
mΩ
nH
ns
µs
V
kHz
db
mV/A
mV/A
mV/A
mV
V/µs
Ω
%
%
%
Fully enabled, input frequency =
1 MHz
—
2.1
—
MODE, R1, R2, R3, R4 inputs
(TTL compatible)
2.0
—
250
—
—
30
Measured from IIN to IOUT
Measured from IIN to IOUT
OUT, OUT1, OUT2 delay relative to
input
Time from VDD = V
UVLO
+ V
HYST
to
cal complete
—
—
—
—
—
50
—
Si85x1/4/7
Si85x2/5/8
Si85x3/6/9
—
—
—
—
—
20
OUT, OUT1, OUT2 Offset Voltage
(V
OUTMIN
)
VOUT Slew Rate
OUT, OUT1, OUT2 Output Resistance
Measurement Error (%)—all devices
(–40 to 85 ºC Temp Range)
Current flow from I
IN
to I
OUT
= 0
OUT, OUT1, OUT2 load = 5K || 50 pF
5 to 10% of full scale
10 to 20% of full scale
20 to 100% of full scale
–20
–10
–5
—
—
—
+20
+10
+5
4
Preliminary Rev. 0.1
Si85xx
Table 1. Electrical Specifications (Continued)
TA = –40 to +85 ºC (typical specified at 25 ºC), VDD = 2.7 to 5.5 V
Parameter
Measurement Error (%)—all devices
(–40 to 125 ºC Temp Range)
Conditions
5 to 10% of full scale
10 to 20% of full scale
20 to 100% of full scale
Min
–30
–25
–20
Typ
—
—
—
Max
+30
+25
+20
Unit
%
%
%
Table 2. Absolute Maximum Ratings
Parameter
Storage temperature
Ambient temperature under bias
Supply voltage
Voltage on any pin with respect to ground
(not including IIN, IOUT)
Lead solder temperature (10 sec.)
DC isolation
Symbol
T
STG
T
A
V
DD
V
IN
-
-
–0.5
Min
–65
–40
Typ
Max
+150
+125
5.75
VDD + 0.5
260
1000
Units
ºC
ºC
V
V
ºC
VDC
Note:
Permanent device damage may occur if the above Absolute Maximum Ratings are exceeded. Functional operation
should be restricted to conditions as specified in the operational sections of this data sheet. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
Preliminary Rev. 0.1
5
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