MAX745 [MAXIM]
Switch-Mode Lithium-Ion Battery-Charger; 开关模式锂离子电池充电器
| 型号： | MAX745 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Switch-Mode Lithium-Ion Battery-Charger |
| 文件： | 总8页 (文件大小：93K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1182; Rev 2; 12/98
S w it c h -Mo d e Lit h iu m -Io n
Ba t t e ry-Ch a rg e r
MAX745
Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The MAX745 p rovid e s a ll func tions ne c e s s a ry for
charging lithium-ion battery packs. It provides a regu-
lated charging current of up to 4A without getting hot,
and a regulated voltage with only ±0.75% total error at
the battery terminals. It uses low-cost, 1% resistors to
set the output voltage, and a low-cost N-channel MOS-
FET as the power switch.
♦ Charges 1 to 4 Lithium-Ion Battery Cells
♦ ±0.75% Voltage-Regulation Accuracy
Using 1% Resistors
♦ Provides up to 4A without Excessive Heating
♦ 90% Efficient
♦ Uses Low-Cost Set Resistors and
N-Channel Switch
The MAX745 regulates the voltage set point and charg-
ing current using two loops that work together to transi-
tion smoothly between voltage and current regulation.
The p e r-c e ll b a tte ry volta g e re g ula tion limit is s e t
between 4.0V and 4.4V using standard 1% resistors,
and then the number of cells is set from 1 to 4 by pin-
strapping. Total output voltage error is less than ±0.75%.
♦ Up to 24V Input
♦ Up to 18V Maximum Battery Voltage
♦ 300kHz PWM Operation: Low-Noise,
Small Components
♦ Stand-Alone Operation; No Microcontroller
Needed
For a similar device with an SMBus™ microcontroller
interface and the ability to charge NiCd and NiMH cells,
refer to the MAX1647 and MAX1648. For a low-cost
lithium-ion c ha rg e r us ing a line a r-re g ula tor c ontrol
scheme, refer to the MAX846A.
________________________Ap p lic a t io n s
Lithium-Ion Battery Packs
Desktop Cradle Chargers
Cellular Phones
Ord e rin g In fo rm a t io n
Notebook Computers
Hand-Held Instruments
PART
MAX745C/D
MAX745EAP
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
Dice*
-40°C to +85°C
20 SSOP
Pin Configuration appears on last page.
*Dice are tested at T = +25°C.
A
___________________________________________________Typ ic a l Op e ra t in g Circ u it
V
IN
(UP TO 24V)
DCIN
VL
BST
DHI
CELL
COUNT
SELECT
CELL0
CELL1
N
N
MAX745
ON
LX
OFF
THM/SHDN
REF
DLO
I
CHARGE
SETI
CS
VADJ
R
SENSE
SET PER
CELL VOLTAGE
WITH 1% RESISTORS
STATUS
BATT
CCV CCI GND IBAT PGND
VOUT
1–4 Li+ CELLS
(UP TO 18V)
SMBus is a trademark of Intel Corp.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
S w it c h -Mo d e Lit h iu m -Io n
Ba t t e ry Ch a rg e r
ABSOLUTE MAXIMUM RATINGS
DCIN to GND ............................................................-0.3V to 26V
BST, DHI to GND ......................................................-0.3V to 30V
BST to LX ....................................................................-0.3V to 6V
DHI to LX............................................(LX - 0.3V) to (BST + 0.3V)
LX to GND ................................................-0.3V to (DCIN + 0.3V)
VL to GND...................................................................-0.3V to 6V
CELL0, CELL1, IBAT, STATUS, CCI, CCV,
BATT, CS to GND .....................................................-0.3V to 20V
PGND to GND..........................................................-0.3V to 0.3V
VL Current...........................................................................50mA
Continuous Power Dissipation (T = +70°C)
A
SSOP (derate 8.00mW/°C above +70°C) ......................640mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature .........................................-60°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
MAX745
REF, SETI, VADJ, DLO, THM/SHDN to GND ..-0.3V to (VL + 0.3V)
Stresses beyond those listed under “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 for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
DCIN
= 18V, V
= 8.4V, T = 0°C to +85°C. Typical values are at T = +25°C, unless otherwise noted.)
BATT
A
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SUPPLY AND REFERENCE
DCIN Input Voltage Range
6
24
6
V
mA
V
DCIN Quiescent Supply Current
VL Output Voltage
6.0V < V
< 24V, logic inputs = VL
< 24V, no load
4
DCIN
6.0V < V
5.15
4.17
4.16
5.40
4.2
4.2
10
5.65
4.23
4.24
20
DCIN
T
A
= +25°C
REF Output Voltage
V
6.0V < V
< 24V
DCIN
REF Output Load Regulation
0 < I
< 1mA
mV/mA
REF
SWITCHING REGULATOR
Oscillator Frequency
DHI Maximum Duty Cycle
DHI On-Resistance
270
89
300
93
4
330
kHz
%
Ω
Output high or low
Output high or low
7
14
5
Ω
DLO On-Resistance
6
VL < 3.2V, V
= 12V
BATT
µA
µA
BATT Input Current
CS Input Current
VL > 5.15V, V
= 12V
500
5
BATT
VL < 3.2V, V = 12V
CS
VL > 5.15V, V = 12V
400
19
CS
BATT, CS Input Voltage Range
4V < V
< 16V
0
V
BATT
CS to BATT Offset Voltage (Note 1)
±1.5
185
18
mV
SETI = V
(full scale)
170
14
205
22
REF
CS to BATT
Current-Sense Voltage
mV
%
SETI = 400mV
Not including VADJ resistor tolerance
With 1% tolerance VADJ resistors
-0.65
-0.75
0.65
0.75
Absolute Voltage Accuracy
2
_______________________________________________________________________________________
S w it c h -Mo d e Lit h iu m -Io n
Ba t t e ry Ch a rg e r
MAX745
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= 18V, V
= 8.4V, T = 0°C to +85°C. Typical values are at T = +25°C, unless otherwise noted.)
BATT
A
A
PARAMETER
ERROR AMPLIFIERS
CONDITIONS
MIN
TYP
MAX
UNITS
µA/V
µA/V
µA
GMV Amplifier Transconductance
GMI Amplifier Transconductance
GMV Amplifier Output Current
800
200
±130
±320
80
µA
GMI Amplifier Output Current
CCI Clamp Voltage with Respect to CCV
CCV Clamp Voltage with Respect to CCI
1.1V < V
< 3.5V
25
25
200
200
mV
mV
CCV
1.1V < V
< 3.5V
80
CCI
CONTROL INPUTS/OUTPUTS
CELL0, CELL1 Input Bias Current
SETI Input Voltage Range (Note 1)
VADJ Adjustment Range
µA
V
-1
0
1
V
REF
10
%
nA
V
SETI, VADJ Input Bias Current
VADJ Input Voltage Range
-10
0
10
V
REF
2.20
2.01
2.3
2.1
2.34
V
THM/SHDN Rising Threshold
THM/SHDN Falling Threshold
2.19
V
Charger in current-regulation mode,
STATUS sinking 1mA
STATUS Output Low Voltage
0.2
V
Charger in voltage-regulation mode,
µA
STATUS Output Leakage Current
1
2
V
= 5V
STATUS
IBAT Output Current vs.
Current-Sense Voltage
µA/mV
V
IBAT
= 2V
0.9
IBAT Compliance Voltage Range
0
V
ELECTRICAL CHARACTERISTICS
(V
DCIN
= 18V, V = 8.4V, T = -40°C to +85°C, unless otherwise noted. Limits over temperature are guaranteed by design.)
BATT A
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SUPPLY AND REFERENCE
VL Output Voltage
6.0V < V
< 24V, no load
< 24V
5.10
4.14
5.70
4.26
V
V
DCIN
REF Output Voltage
6.0V < V
DCIN
SWITCHING REGULATOR (Note 1)
Oscillator Frequency
260
340
7
kHz
Ω
DHI On-Resistance
DLO On-Resistance
Output high or low
Output high or low
Ω
14
CS to BATT Full-Scale
Current-Sense Voltage
165
-1.0
205
1.0
mV
%
Absolute Voltage Accuracy
Not including VADJ resistors
Note 1: When V
= 0V, the battery charger turns off.
SETI
_______________________________________________________________________________________
3
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__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(T = +25°C, V
= 18V, V
= 4.2V, CELL0 = CELL1 = GND, C = 4.7µF, C = 0.1µF. Circuit of Figure 1, unless
REF
A
DCIN
BATT
VL
otherwise noted.)
BATTERY VOLTAGE
vs. CHARGING CURRENT
CURRENT-SENSE VOLTAGE
vs. SETI VOLTAGE
4.5
200
R1 = 0.2Ω
180
160
4.0
3.5
MAX745
140
120
3.0
2.5
100
80
2.0
1.5
1.0
0.5
60
40
R1 = 0.2Ω
R16 = SHORT
R12 = OPEN CIRCUIT
20
0
0
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
CHARGING CURRENT (A)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
SETI VOLTAGE (V)
REFERENCE VOLTAGE
vs. TEMPERATURE
VOLTAGE LIMIT
vs. VADJ VOLTAGE
4.205
4.204
4.203
4.45
4.40
4.35
4.30
4.25
4.20
4.15
4.10
4.05
4.00
3.95
4.202
4.201
4.200
4.199
4.198
4.197
4.196
4.195
0
25
50
75
100
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
VADJ VOLTAGE (V)
TEMPERATURE (°C)
VL LOAD REGULATION
REFERENCE LOAD REGULATION
5.50
5.45
5.40
4.25
4.24
4.23
5.35
5.30
5.25
5.20
5.15
5.10
4.22
4.21
4.20
4.19
4.18
4.17
4.16
4.15
5.05
0
0
5
10
15
20
25
0
500 1000 1500 2000 2500 3000
VL OUTPUT CURRENT (mA)
REFERENCE CURRENT (µA)
4
_______________________________________________________________________________________
S w it c h -Mo d e Lit h iu m -Io n
Ba t t e ry Ch a rg e r
MAX745
______________________________________________________________P in De s c rip t io n
PIN
NAME
FUNCTION
Current-Sense Amplifier’s Analog Current-Source Output. See Monitoring Charge Current section for
detailed description.
1
IBAT
2
3
4
5
DCIN
VL
Charger Input Voltage. Bypass DCIN with a 0.1µF capacitor.
Chip Power Supply. Output of the 5.4V linear regulator from DCIN. Bypass VL with a 4.7µF capacitor.
Voltage-Regulation-Loop Compensation Point
CCV
CCI
Current-Regulation-Loop Compensation Point
THM/
SHDN
Thermistor Sense-Voltage Input. THM/SHDN also performs the shutdown function. If pulled low,
the charger turns off.
6
7
8
REF
4.2V Reference Voltage Output. Bypass REF with a 0.1µF or greater capacitor.
Voltage-Adjustment Pin. VADJ is tied to a 1% tolerance external resistor-divider to adjust the voltage set
point by 10%, eliminating the need for precision 0.1% resistors. The input voltage range is 0V to V
VADJ
.
REF
9
SETI
GND
SETI is externally tied to the resistor-divider between REF and GND to set the charging current.
Analog Ground
10
CELL1,
CELL0
11, 12
Logic Inputs to Select Cell Count. See Table 1 for cell-count programming.
An open-drain MOSFET sinks current when in current-regulation mode, and is high impedance when in volt-
age-regulation mode. Connect STATUS to VL through a 1kΩ to 100kΩ pull-up resistor. STATUS may also drive
an LED for visual indication of regulation mode (see MAX745 evaluation kit). Leave STATUS floating if not used.
13
STATUS
14
15
16
17
18
19
20
BATT
CS
Battery-Voltage-Sense Input and Current-Sense Negative Input
Current-Sense Positive Input
PGND
DLO
DHI
Power Ground
Low-Side Power MOSFET Driver Output
High-Side Power MOSFET Driver Output
Power Connection for the High-Side Power MOSFET Source
Power Input for the High-Side Power MOSFET Driver
LX
BST
current-regulation limit before the voltage limit, causing
_______________De t a ile d De s c rip t io n
the system to regulate current. As the battery charges,
the voltage rises to the point where the voltage limit is
reached and the charger switches to regulating volt-
age. The STATUS pin indicates whether the charger is
regulating current or voltage.
The MAX745 is a s witc h-mod e , lithium-ion b a tte ry
charger that can achieve 90% efficiency. The charge
voltage and current are set independently by external
resistor-dividers at SETI and VADJ, and at pin connec-
tions at CELL0 and CELL1. VADJ is connected to a
resistor-divider to set the charging voltage. The output
voltage-adjustment range is ±5%, eliminating the need
for 0.1% resistors while still achieving 0.75% set accu-
racy using 1% resistors.
Vo lt a g e Co n t ro l
To set the voltage limit on the battery, tie a resistor-
divider to VADJ from REF. A 0V to V
change at
REF
VADJ sets a ±5% change in the battery limit voltage
around 4.2V. Since the 0 to 4.2V range on VADJ results
in only a 10% change on the voltage limit, the resistor-
divider’s accuracy does not need to be as high as the
output voltage accuracy. Using 1% resistors for the
voltage dividers typically results in no more than 0.1%
degradation in output voltage accuracy. VADJ is inter-
nally buffered so that high-value resistors can be used
to set the output voltage. When the voltage at VADJ is
The MAX745 consists of a current-mode, pulse-width-
modulated (PWM) controller and two transconductance
error amplifiers: one for regulating current (GMI) and
the other for regulating voltage (GMV) (Figure 2). The
error amplifiers are controlled via the SETI and VADJ
pins. Whether the MAX745 is controlling voltage or cur-
rent at any time depends on the battery state. If the bat-
tery is discharged, the MAX745 output reaches the
_______________________________________________________________________________________
5
S w it c h -Mo d e Lit h iu m -Io n
Ba t t e ry Ch a rg e r
V
REF
/ 2, the voltage limit is 4.2V. Table 1 defines the
whe re V
= 4.2V a nd c e ll c ount is 1, 2, 3, or 4
REF
battery cell count.
(Table 1).
The battery limit voltage is set by the following:
The voltage-regulation loop is compensated at the CCV
pin. Typically, a series-resistor-capacitor combination
can be used to form a pole-zero doublet. The pole
introduced rolls off the gain starting at low frequencies.
The zero of the doublet provides sufficient AC gain at
mid-frequencies. The output capacitor (C1) rolls off the
mid-frequency gain to below unity. This guarantees sta-
bility before encountering the zero introduced by the
C1’s e q uiva le nt s e rie s re s is ta nc e (ESR). The GMV
amplifier’s output is internally clamped to between one-
fourth and three-fourths of the voltage at REF.
1
V
−
V
REF
ADJ
2
V
=
cell count x V
+
(
)
BATT
REF
9.523
MAX745
Solving for V
, we get:
ADJ
9.523 V
BATT
V
=
− 9.023V
REF
ADJ
cell count
(
)
Set V
and determine R3 by:
by choosing a value for R11 (typically 100k),
Cu rre n t Co n t ro l
The charging current is set by a combination of the cur-
rent-sense resistor value and the SETI pin voltage. The
current-sense amplifier measures the voltage across
the current-sense resistor, between CS and BATT. The
current-sense amplifier’s gain is 6. The voltage on SETI
is buffered and then divided by 4. This voltage is com-
p a re d to the c urre nt-s e ns e a mp lifie r’s outp ut.
Therefore, full-scale current is accomplished by con-
necting SETI to REF. The full-scale charging current
ADJ
R3 = [1 - (V
/ V )] x R11 (Figure 1)
ADJ
REF
Table 1. Cell-Count Programming Table
CELL0
GND
VL
CELL1
GND
GND
VL
CELL COUNT
1
2
3
4
(I
FS)
is set by the following:
GND
VL
I
FS
= 185mV / R1 (Figure 1)
VL
(UP TO 24V)
V
IN
D2
C6
0.1µF
C5
4.7µF
IN4148
VL
DCIN
BST
REF
C7
0.1µF
M1A
1/2 IRF7303
R15
10k
R16
R12
L1
22µH
DHI
LX
C4
0.1µF
THM/SHDN
R3
100k
1%
MAX745
1/2 IRF7303
M1B
THM 1
D6
MBRS
340T3
D1
DLO
MBRS
340T3
SETI
PGND
CS
0.2Ω
R1
VADJ
R2
10k
C2, 0.1µF
BATT
C1
68µF
CCV
CCI
R11
100k
1%
BATTERY
STATUS
IBAT
GND
C3
47nF
Figure 1. Standard Application Circuit
_______________________________________________________________________________________
6
S w it c h -Mo d e Lit h iu m -Io n
Ba t t e ry Ch a rg e r
MAX745
To s e t c urre nts b e low full s c a le without c ha ng ing
R1, adjust the voltage at SETI according to the follow-
ing formula:
R
must be chosen to limit V
to voltages below
IBAT
IBAT
2V for the maximum charging current. Connect IBAT to
GND if unused.
I
= I (V
/ V
)
SETI
REF
CHG
FS
P WM Co n t ro lle r
The b a tte ry volta g e or c urre nt is c ontrolle d b y a
current-mode, PWM DC/DC converter controller. This
controller drives two external N-channel MOSFETs,
which control power from the input source. The con-
troller sets the switched voltage’s pulse width so that it
supplies the desired voltage or current to the battery.
Tota l c omp one nt c os t is re d uc e d b y us ing a d ua l,
N-channel MOSFET.
A capacitor at CCI sets the current-feedback loop’s
dominant pole. While the current is in regulation, CCV
voltage is clamped to within 80mV of the CCI voltage.
This prevents the battery voltage from overshooting
when the voltage setting is changed. The converse is
true when the voltage is in regulation and the current
setting is changed. Since the linear range of CCI or
CCV is about 2V (1.5V to 3.5V), the 80mV clamp results
in negligible overshoot when the loop switches from
voltage regulation to current regulation, or vice versa.
The heart of the PWM controller is a multi-input com-
parator. This comparator sums three input signals to
determine the switched signal’s pulse width, setting the
battery voltage or current. The three signals are the
current-sense amplifier’s output, the GMV or GMI error
amplifier’s output, and a slope-compensation signal
that ensures that the current-control loop is stable.
Mo n it o rin g Ch a rg e Cu rre n t
The battery-charging current can be externally moni-
tored by placing a scaling resistor (R
IBAT and GND. IBAT is the output of a voltage-con-
trolled current source, with output current given by:
) between
IBAT
The PWM c omp a ra tor c omp a re s the c urre nt-s e ns e
amplifier’s output to the lower output voltage of either
the GMV or GMI amplifiers (the error voltage). This cur-
rent-mode feedback reduces the effect of the inductor
on the output filter LC formed by the output inductor
(L1) and C1 (Figure 1). This makes stabilizing the cir-
cuit much easier, since the output filter changes to a
first-order RC from a complex, second-order RLC.
I
= 0.9µA/V
SENSE
BAT
where V
is the voltage across the current-sense
resistor (in millivolts) given by:
SENSE
V
= V - V
= I
x R1
SENSE
CS
BATT
CHG
The voltage across R
is then given by:
IBAT
R
0.9µA
IBAT
R
1
V
=
x
IBAT
I
CHG
IBAT
DCIN
CURRENT
SENSE
BATT
CS
5.4V
REG
4.2
REF
REF
A = 6
V
ON
VL
STATUS
GMI
1
/
SETI
CCI
4
BST
DHI
LX
PWM
VL
LOGIC
CLAMP
DLO
PGND
THM/SHDN
GMV
VADJ
CCV
REF
2
CELL0
CELL1
CELL
LOGIC
GND
Figure 2. Functional Diagram
_______________________________________________________________________________________
7
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MOS FET Drive rs
The MAX745 drives external N-channel MOSFETs to
switch the input source generating the battery voltage or
current. Since the high-side N-channel MOSFET’s gate
must be driven to a voltage higher than the input source
voltage, a charge pump is used to generate such a volt-
age. The capacitor (C7) charges through D2 to approxi-
mately 5V when the synchronous rectifier (M1B) turns on
(Figure 1). Since one side of C7 is connected to LX (the
source of M1A), the high-side driver (DHI) drives the gate
up to the voltage at BST, which is greater than the input
voltage while the high-side MOSFET is on.
Min im u m In p u t Vo lt a g e
The input voltage to the charger circuit must be greater
than the maximum battery voltage by approximately 2V
so the charger can regulate the voltage properly. The
input voltage can have a large AC-ripple component
when operating from a wall cube. The voltage at the low
point of the ripple waveform must still be approximately
2V greater than the maximum battery voltage.
MAX745
Using components as indicated in Figure 1, the minimum
input voltage can be determined by the following formula:
[V
+ V + I (
CHG
R
+ R + R1)]
L
DS(ON)
BATT
D6
V
IN
x
0.89
where: V is the input voltage;
The synchronous rectifier (M1B) behaves like a diode
but has a smaller voltage drop, improving efficiency. A
small dead time is added between the time when the
high-side MOSFET is turned off and when the synchro-
nous re c tifie r is turne d on, a nd vic e ve rs a . This
prevents crowbar currents during switching transitions.
Place a Schottky rectifier from LX to ground (D1, across
M1B’s drain and source) to prevent the synchronous
rectifier’s body diode from conducting during the dead
time. The body diode typically has slower switching-
recovery times, so allowing it to conduct degrades
e ffic ie nc y. D1 c a n b e omitte d if e ffic ie nc y is not a
concern, but the resulting increased power dissipation
in the synchronous rectifier must be considered.
IN
V
D6
is the voltage drop across D6
(typically 0.4V to 0.5V);
I
is the charging current;
CHG
R
is the high-side
DS(ON)
MOSFET M1A’s on-resistance;
R is the the inductor’s series resistance;
L
R1 is the current-sense resistor R1’s value.
__________________P in Co n fig u ra t io n
Since the BST capacitor is charged while the synchro-
nous rectifier is on, the synchronous rectifier may not be
replaced by a rectifier. The BST capacitor will not fully
charge without the synchronous rectifier, leaving the high-
side MOSFET with insufficient gate drive to turn on.
However, the synchronous rectifier can be replaced with
a small MOSFET (such as a 2N7002) to guarantee that
the BST capacitor is allowed to charge. In this case, the
majority of the high charging currents are carried by D1,
and not by the synchronous rectifier.
TOP VIEW
IBAT
DCIN
BST
20
1
2
3
4
5
6
7
8
9
19 LX
VL
18 DHI
17 DLO
16 PGND
CCV
MAX745
CCI
THM/SHDN
REF
15
14
13
CS
BATT
STATUS
In t e rn a l Re g u la t o r a n d Re fe re n c e
The MAX745 uses an internal low-dropout linear regula-
tor to create a 5.4V power supply (VL), which powers its
internal circuitry. The VL regulator can supply up to
25mA. Since 4mA of this current powers the internal cir-
cuitry, the remaining 21mA can be used for external cir-
c uitry. MOSFET g a te -d rive c urre nt c ome s from VL,
which must be considered when drawing current for
other functions. To estimate the current required to drive
the MOSFETs, multiply the sum of the MOSFET gate
charges by the switching frequency (typically 300kHz).
Bypass VL with a 4.7µF capacitor to ensure stability.
VADJ
SETI
12 CELL0
11 CELL1
GND 10
SSOP
___________________Ch ip In fo rm a t io n
TRANSISTOR COUNT: 1695
SUBSTRATE CONNECTED TO GND
The MAX745 internal 4.2V reference voltage must be
bypassed with a 0.1µF or greater capacitor.
8
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