RT9554A - Richtek

®
RT9554A
Battery Output Current Sense Protection IC
General Description
Features
The RT9554A is designed for over-current detection. The
current sense amplifier amplifies the voltage across resistor
which is connected between CSP and CSN by 200. The
amplified voltage is compared with the voltage of BAT_REF
and check whether over-current happens or not. The
RT9554A also provides a comparator with two input pins,
AC_REAL and AC_REF for users. There is an output pin
FLAG as an indicator which is a N-MOSFET in open-drain
configuration. Users can connect one resistor between
the FLAG pin and supply voltage. Either over-current
condition occurs or the AC_REAL voltage is larger than
the AC_REF voltage, the FLAG is pulled low. The RT9554A
is a available in the WDFN-8L 2x2 package.

Common Mode Input Range up to 24V

VCC Operating Current : 200μA
μA (under S3/S4/S5)
VCC Shutdown Current : 5μ
Programmable Over-Current Level
FLAG Signal goes Low when OCP
RoHS Compliant and Halogen Free




Applications

Notebooks
Pin Configurations
VCC
EN
FLAG
AC_REF
Ordering Information
RT9554A
Package Type
QW : WDFN-8L 2x2 (W-Type)
9
8
7
6
5
CSP
CSN
BAT_REF
AC_REAL
WDFN-8L 2x2
Lead Plating System
G : Green (Halogen Free and Pb Free)
Marking Information
Note :
2C : Product Code
Richtek products are :

1
2
3
4
GND
(TOP VIEW)
2CW
RoHS compliant and compatible with the current require-
W : Date Code
ments of IPC/JEDEC J-STD-020.

Suitable for use in SnPb or Pb-free soldering processes.
Simplified Application Circuit
RSENSE
Output
Input
1.05V
RT9554A
FLAG
CSN
3.3V
CSP
VCC
5V
0V
EN
BAT_REF
AC_REAL
AC_REF
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RT9554A
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
VCC
Power Supply Input. Connect this pin to 5V and place a minimum 0.1F
decoupling capacitor .The decoupling capacitor should be placed to this pin
as close as possible.
2
EN
Enable Control Input.
3
FLAG
Open-Drain Output. Connected to an external resistor. When over-current
occurs, this pin will be pulled low.
4
AC_REF
Comparator Inverting Input.
5
AC_REAL
Comparator Non-Inverting Input.
6
BAT_REF
Over-Current Threshold Setting. It is used to set over-current threshold from
0.4V to 2V.
7
CSN
Negative Current Sense Input.
8
CSP
Positive Current Sense Input.
9 (Exposed Pad)
GND
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation
Function Block Diagram
POR
+
x 200
-
CSP
CSN
VRON
EN
Comparator
VCC
+
BAT_REF
FLAG
-
Comparator
AC_REAL
+
AC_REF
-
GND
Operation
The RT9554A consists of one current sensing amplifier
and one comparator, and it provides the following
functions : over-current protection and voltage comparison
between AC_REAL and AC_REF. Users can connect one
resistor between the FLAG pin and supply voltage. Either
over-current condition or the occurs AC_REAL voltage is
larger than AC_REF, the FLAG pin is pulled low.
Over Current Protection
BAT_REF voltage. If the output voltage of current sensing
amplifier is larger than the BAT_REF voltage, the FLAG
pin is pulled low.
AC_REAL & AC_REF Comparison
A comparator is designed for the voltage comparison
between AC_REAL and AC_REF. If the voltage of
AC_REAL is larger than AC_REF, the FLAG pin is pulled
low.
With 1mΩ order of resistor shunts between CSP and CSN,
the current sensing amplifier amplifies the voltage between
CSP and CSN by 200 and compares the result with the
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is a registered trademark of Richtek Technology Corporation.
DS9554A-00 June 2014
RT9554A
Absolute Maximum Ratings








(Note 1)
CSP/CSN to GND --------------------------------------------------------------------------------------------------------- −0.3V to 26V
VCC, BAT_REF, EN, AC_REAL, AC_REF, FLAG to GND ------------------------------------------------------- −0.3V to 6V
Power Dissipation, PD @ TA = 25°C
WDFN-8L 2x2 -------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WDFN-8L 2x2, θJA --------------------------------------------------------------------------------------------------------WDFN-8L 2x2, θJC -------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------------MM (Machine Model) -----------------------------------------------------------------------------------------------------
Recommended Operating Conditions




2.19W
45.5°C/W
11.5°C/W
260°C
150°C
−65°C to 150°C
2kV
200V
(Note 4)
High-Side Voltage, VCSP/VCSN -------------------------------------------------------------------------------------Supply Voltage, VCC ----------------------------------------------------------------------------------------------------Junction Temperature Range -------------------------------------------------------------------------------------------Ambient Temperature Range --------------------------------------------------------------------------------------------
4.5V to 24V
4.5V to 5.5V
−40°C to 125°C
−40°C to 85°C
Electrical Characteristics
(VCC = 5V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
5
--
24
V
EN = High
--
50
--
A
EN = Low
--
--
5
A
CSN CSP Input
Input Voltage Range
V CSP, VCSN
ICSN + ICSP
VCC Input
VCC Operating Current
I VCC
VCC > POR, EN = High
--
200
--
A
VCC Shutdown Current
I VCC_shd
VCC > POR, EN = Low
--
2
5
A
VCC POR Rising Voltage
V IN_POR
2.8
--
3.7
V
--
400
--
mV
Rising
Hysteresis
Enable
Enable Input
Voltage
Logic-High
V IH
0.7
--
--
V
Logic-Low
V IL
--
--
0.3
V
Current Sense Circuit
System Response Time
OCdelay
OCP triggered
--
50
--
s
OP Gain
AV
VCSP = VCSN = 12V
--
200
--
V/V
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RT9554A
Parameter
Symbol
Min
Typ
Max
Unit
ISINK = 10mA
--
--
0.1
V
VBAT_REF = 0.4V
--
--
15
%
VBAT_REF = 0.8V
--
--
10
%
VBAT_REF = 2V
--
--
5
%
Ileak_FLAG
EN Low
--
--
5
A
BAT_REF Leakage Current
Ileak_BAT_REF
EN Low
--
--
5
A
BAT_REF Input Range
VBAT_REF
0.4
--
2
V
--
--
10
mV
FLAG Pull Low Voltage
Input Current Sensing
Accuracy
FLAG Leakage Current
CSacc
Test conditions
OCSET Comparator
AC_REAL & AC_REF Comparator
Comparator Offset
VOS_AL_CMP
AC_REAL Input Range
VAC_REAL
0.3
--
2
V
AC_REF Input Range
VAC_REF
0.3
--
2
V
--
--
200
ns
Comparator Response Time
VAC_REAL = 0.3V to 2V
VAC_REAL > VAC_REF
FLAG go low
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
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RT9554A
Typical Application Circuit
ISENSE
Output
Input
1.05V
0.001
RT9554A
7
0.1µF
10k
CSN
FLAG
0.1µF
3
3.3V
8 CSP
0.1µF
R1
BAT_REF
2.2
1
5V
VCC
0.1µF
1k
5V
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AC_REAL
4
9 (Exposed Pad)
EN
0.1µF
From System
R2
GND
2
6
5
From System
AC_REF
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RT9554A
Typical Operating Characteristics
FLAG Behavior
FLAG Behavior
AC_REF
(1V/Div)
AC_REF
(1V/Div)
AC_REAL
(2V/Div)
AC_REAL
(2V/Div)
FLAG
(1V/Div)
FLAG
(1V/Div)
AC_REF = 1V, AC_REAL from 0 to 5V
Time (100ns/Div)
Time (400ns/Div)
FLAG Behavior
FLAG Behavior
I LOAD
(5A/Div)
I LOAD
(5A/Div)
BAT_REF
(500mV/Div)
BAT_REF
(500mV/Div)
FLAG
(1V/Div)
AC_REF = 1V, AC_REAL from 5 to 0V
BAT_REF = 1V, ILOAD = 0A to 6A
FLAG
(1V/Div)
BAT_REF = 1V, ILOAD = 6A to 0A
Time (10μs/Div)
Time (10μs/Div)
Power On Mask Time
Power Off from EN
I LOAD
(5A/Div)
I LOAD
(5A/Div)
FLAG
(2V/Div)
FLAG
(2V/Div)
BAT_REF
(900mV/Div)
BAT_REF
(500mV/Div)
EN
(5V/Div)
BAT_REF = 1V, ILOAD = 0A to 6A
Time (1ms/Div)
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EN
(5V/Div)
BAT_REF = 1V, ILOAD = 0A to 6A
Time (500μs/Div)
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DS9554A-00 June 2014
RT9554A
OCP Accuracy Curve
0
-1
Accuracy (%)
-2
-3
-4
-5
-6
-7
-8
-9
VIN = 12V, RS = 1mΩ
-10
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
BAT_REF (V)
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RT9554A
Application Information
The RT9554A provides battery OCP protection functions
with FLAG indicator to informs system. It can operate
with minimized external components of switching power
supply systems to achieve OCP protection. The overcurrent is detected by monitoring the differential voltage
of input current sense resistor. The RT9554A provides a
50μs system response time for FLAG and there is a 3ms
mask time after EN rising edge. Also, the RT9554A
provides a comparator with two pins, AC_REAL and
AC_REF for users.
FLAG
The FLAG is an open-drain output and requires a pull-up
resistor. When over-current is detected, FLAG is pulled
low within 50μs and maintain until OCP status releases.
Over Current Protection( OCP)
As an industry standard, high accuracy current sense
amplifier is used to monitor the input current that flow
through current sense resistor, The RT9554A detects CSPCSN differential voltage across the current sense resistor
to monitor input current from battery. The OCP trigger
point equation is shown as below :
R2
R1  R2
ISENSE  0.001  200 = BAT_REF
BAT_REF  3.3V 
200 is the internal error amp AV.
We suggest R1+ R2 = 100kΩ to avoid power consumption.
Isense is over-current protection trigger point.
For the overall timing sequence, please refer to Figure 1.
Filter capacitor
A 0.1μF capacitor between CSP and CSN for differential
mode filtering is recommended. A 0.1μF capacitor between
CSN and ground is for common mode filtering, and an
optional 0.1μF capacitor between CSP and ground is for
common mode filtering.
The CSP and CSN pins are used to sense Rsense with
default value of 1mΩ. However, resistors of other values
can also be used. Using a larger sense resistor, can have
higher regulation accuracy, but, it comes with higher
conduction loss.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
WDFN-8L 2x2 package, the thermal resistance, θJA, is
45.5°C/W on a standard JEDEC 51-7 four-layer thermal
test board. The maximum power dissipation at TA = 25°C
can be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (45.5°C/W) = 2.19W for
WDFN-8L 2x2 package
VCC
3ms
EN
BAT_REF
VOC
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. The derating curve in Figure 2 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
FLAG
Figure 1. Timing Sequence
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RT9554A
Maximum Power Dissipation (W)1
2.8
Four-Layer PCB
Layout Considerations
1.6
Layout is very important for the RT9554A. If designed
improperly, the PCB may radiate excessive noise. Certain
points must be considered before starting a layout for the
RT9554A.
1.2

Connect an RC low pass filter to VCC, 0.1μF, and 2.2Ω
are recommended Connect a RC low pass filter to EN,
0.1μF, and 1kΩ are recommended. Place the filter
capacitor close to the IC.

Current sense connections must always be made using
Kelvin connections to ensure an accurate signal with
the current limit resistor located at the device.

All sensitive analog traces and components such as
CSP, CSN, VCC, EN and FLAG , should be placed away
form high voltage switching nodes to avoid coupling.
2.4
2.0
0.8
0.4
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 2. Derating Curve of Maximum Power Dissipation
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RT9554A
Outline Dimension
D2
D
L
E
E2
1
e
SEE DETAIL A
b
2
1
2
1
A
A1
A3
DETAIL A
Pin #1 ID and Tie Bar Mark Options
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.200
0.300
0.008
0.012
D
1.950
2.050
0.077
0.081
D2
1.000
1.250
0.039
0.049
E
1.950
2.050
0.077
0.081
E2
0.400
0.650
0.016
0.026
e
L
0.500
0.300
0.020
0.400
0.012
0.016
W-Type 8L DFN 2x2 Package
Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek 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 Richtek or its subsidiaries.
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