MIC2182-3.3BSM [MICROCHIP]
SWITCHING CONTROLLER, 330kHz SWITCHING FREQ-MAX, PDSO16;型号: | MIC2182-3.3BSM |
厂家: | MICROCHIP |
描述: | SWITCHING CONTROLLER, 330kHz SWITCHING FREQ-MAX, PDSO16 信息通信管理 开关 光电二极管 |
文件: | 总28页 (文件大小:232K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
MIC2182
High-Efficiency Synchronous Buck Controller
General Description
Features
Micrel’s MIC2182 is a synchronous buck (step-down) switch-
ing regulator controller. An all N-channel synchronous archi-
tecture and powerful output drivers allow up to a 20A output
current capabilty. The PWM and skip-mode control scheme
allows efficiency to exceed 95% over a wide range of load
current, making it ideal for battery powered applications, as
well as high current distributed power supplies.
• 4.5V to 32V Input voltage range
• 1.25V to 6V Output voltage range
• 95% efficiency
• 300kHz oscillator frequency
• Current sense blanking
• 5Ω impedance MOSFET Drivers
• Drives N-channel MOSFETs
• 600µA typical quiescent current (skip-mode)
The MIC2182 operates from a 4.5V to 32V input and can
operate with a maximum duty cycle of 86% for use in low-
dropout conditions. It also features a shutdown mode that
reduces quiescent current to 0.1µA.
• Logic controlled micropower shutdown (I < 0.1µA)
• Current-mode control
Q
• Cycle-by-cycle current limiting
• Built-in undervoltage protection
• Adjustable undervoltage lockout
• Easily synchronizable
• Precision 1.245V reference output
• 0.6% total regulation
• 16-pin SOP and SSOP packages
• Frequency foldback overcurrent protection
• Sustained short-circuit protection at any input voltage
• 20A output current capability
The MIC2182 achieves high efficiency over a wide output
current range by automatically switching between PWM and
skip mode. Skip-mode operation enables the converter to
maintain high efficiency at light loads by turning off circuitry
pertaining to PWM operation, reducing the no-load supply
current from 1.6mA to 600µA. The operating mode is inter-
nally selected according to the output load conditions. Skip
mode can be defeated by pulling the PWM pin low which
reduces noise and RF interference.
Applications
The MIC2182 is available in a 16-pin SOP (small-outline
package) and SSOP (shrink small-outline package) with an
operating range from –40°C to +85°C.
• DC power distribution systems
• Notebook and subnotebook computers
• PDAs and mobile communicators
• Wireless modems
• Battery-operated equipment
Typical Application
C11
22uf
35V
VIN
D2
MIC2182-3.3BSM
4.5V to 30V*
11 SD103BWS
10
VIN
VDD
C9
4.7µF
16V
x2
C5
0.1µF
R7
14
BST
C6
0.1µF
100k
6
16
L1
EN/UVLO HSD
Q2*
VOUT
3.3V/4A
R2
0.02Ω
10µH
Si4884
2
15
13
12
8
PWM
VSW
LSD
C4
C7
D1
B140
1nF
Q1*
220uf
Si4884
10V ×2
1
3
5
SS
PGND
CSH
GND
COMP
SYNC
C13, 1nF
R1
2k
9
C3
0.1µF
VOUT
VREF
7
* 30V maximum input voltage limit is due
to standard 30V MOSFET selection.
C2
2.2nF
SGND
C1
0.1µF
See “Application Information” section for
5V to 3.3V/10A and other circuits.
4
GND
4.5V–30V* to 3.3V/4A Converter
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
M9999-042204
April 22, 2004
1
MIC2182
Micrel
Ordering Information
Part Number
Voltage
Adjustable
3.3V
Temperature Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package
Lead Finish
Standard
Standard
Standard
Standard
Standard
Standard
Pb-Free
Pb-Free
Pb-Free
Pb-Free
Pb-Free
Pb-Free
MIC2182BM
16-pin narrow SOP
16-pin narrow SOP
16-pin narrow SOP
16-pin narrow SSOP
16-pin narrow SSOP
16-pin narrow SSOP
16-pin narrow SOP
16-pin narrow SOP
16-pin narrow SOP
16-pin narrow SSOP
16-pin narrow SSOP
16-pin narrow SSOP
MIC2182-3.3BM
MIC2182-5.0BM
MIC2182BSM
5.0V
Adjustable
3.3V
MIC2182-3.3BSM
MIC2182-5.0BSM
MIC2182YM
5.0V
Adjustable
3.3V
MIC2182-3.3YM
MIC2182-5.0YM
MIC2182YSM
5.0V
Adjustable
3.3V
MIC2182-3.3YSM
MIC2182-5.0YSM
5.0V
Pin Configuration
MIC2182
MIC2182-x.x
SS
PWM
1
2
3
4
5
6
7
8
16 HSD
SS
PWM
1
2
3
4
5
6
7
8
16 HSD
15 VSW
14 BST
13 LSD
12 PGND
11 VDD
10 VIN
15 VSW
14 BST
13 LSD
12 PGND
11 VDD
10 VIN
COMP
SGND
SYNC
COMP
SGND
SYNC
EN/UVLO
FB
EN/UVLO
VREF
CSH
9
VOUT
CSH
9 VOUT
Adjustable
16-pin SOP (M)
16-Pin SSOP (SM)
Fixed
16-pin SOP (M)
16-Pin SSOP (SM)
M9999-042204
2
April 22, 2004
MIC2182
Micrel
Pin Description
Pin Number
Pin Name
Pin Function
1
SS
Soft-Start (External Component): Connect external capacitor to ground to
reduce inrush current by delaying and slowing the output voltage rise time.
Rise time is controlled by an internal 5µA current source that charges an
external capacitor to VDD
.
2
3
4
5
PWM
COMP
SGND
SYNC
PWM/Skip-Mode Select (Input): Low sets PWM-mode operation. 1nF
capacitor to ground sets automatic PWM/skip-mode selection.
Compensation (Output): Internal error amplifier output. Connect to capacitor
or series RC network to compensate the regulator control loop.
Small Signal Ground (Return): Route separately from other ground traces to
the (–) terminal of COUT
.
Frequency Synchronization (Input): Optional. Connect to external clock
signal to synchronize the oscillator. Leading edge of signal above the
threshold terminates the switching cycle. Connect to SGND if unused.
6
EN/UVLO
Enable/Undervoltage Lockout (Input): Low-level signal powers down the
controller. Input below the 2.5V threshold disables switching and functions
as an accurate undervoltage lockout (UVLO). Input below the threshold
forces complete micropower (< 0.1µA) shutdown.
7 (fixed)
7 (adj)
8
VREF
FB
Reference Voltage (Output): 1.245V output. Requires 0.1µf capacitor to
ground.
Feedback (Input): Regulates FB pin to 1.245V. See “Application Information”
for resistor divider calculations.
CSH
Current-Sense High (Input): Current-limit comparator noninverting input. A
built-in offset of 100mV between CSH and VOUT pins in conjunction with the
current-sense resistor set the current-limit threshold level. This is also the
positive input to the current sense amplifier.
9
VOUT
Current-Sense Low (Input): Output voltage feedback input and inverting
input for the current limit comparator and the current sense amplifier.
10
11
VIN
[Battery] Unregulated Input (Input): +4.5V to +32V supply input.
VDD
5V Internal Linear-Regulator (Output): VDD is the external MOSFET gate
drive supply voltage and an internal supply bus for the IC. Bypass to SGND
with 4.7µF. VDD can supply up to 5mA for external loads.
12
13
14
PGND
LSD
MOSFET Driver Power Ground (Return): Connects to source of synchro-
nous MOSFET and the (–) terminal of CIN
Low-Side Drive (Output): High-current driver output for external synchronous
MOSFET. Voltage swing is between ground and VDD
.
BST
Boost (Input): Provides drive voltage for the high-side MOSFET driver. The
drive voltage is higher than the input voltage by VDD minus a diode drop.
15
16
VSW
HSD
Switch (Return): High-side MOSFET driver return.
High-Side Drive (Output): High-current driver output for high-side MOSFET.
This node voltage swing is between ground and VIN + 5V – Vdiode drop
.
April 22, 2004
3
M9999-042204
MIC2182
Micrel
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Analog Supply Voltage (V ) .......................................+34V
Analog Supply Voltage (V ) ........................ +4.5V to +32V
IN
IN
Digital Supply Voltage (V ) .........................................+7V
Ambient Temperature (T ) ......................... –40°C to +85°C
DD
A
Driver Supply Voltage (B ) ....................................V +7V
Junction Temperature (T ) ....................... –40°C to +125°C
ST
IN
J
Sense Voltage (V
, C ) ............................. 7V to –0.3V
Package Thermal Resistance
OUT
SH
SOP (θ ) ..........................................................100°C/W
Sync Pin Voltage (V
) ................................ 7V to –0.3V
JA
SYNC
SSOP (θ )........................................................150°C/W
JA
Enable Pin Voltage (V
) ...................................... V
IN
EN/UVLO
Power Dissipation (P )
D
SOP................................................ 400mW @ T = 85°C
A
SSOP ............................................. 270mW @ T = 85°C
A
Ambient Storage Temperature (T ) ......... –65°C to +150°C
S
ESD, Note 3
Electrical Characteristics
VIN = 15V; SS = open; VPWM = 0V; VSHDN = 5V; ILOAD = 0.1A; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C; Note 4; unless
noted
Parameter
Condition
Min
Typ
Max
Units
MIC2182 [Adjustable], (Note 5)
Feedback Voltage Reference
Feedback Voltage Reference
Feedback Voltage Reference
Feedback Bias Current
Output Voltage Range
Output Voltage Line Regulation
Output Voltage Load Regulation
Output Voltage Total Regulation
MIC2182-3.3
1.233
1.220
1.208
1.245
1.245
1.245
10
1.257
1.270
1.282
V
V
4.5V < VIN < 32V, 0 < VCSH – VOUT < 75mV
V
nA
V
1.25
6
VIN = 4.5V to 32V, VCSH – VOUT = 50mV
0.03
0.5
%/V
%
25mV < (VCSH – VOUT) < 75mV (PWM mode only)
0mV < (V
– V
) < 75mV (full load range) 4.5V < V < 32V
0.6
%
CSH
OUT
IN
Output Voltage
3.267
3.234
3.201
3.3
3.3
3.333
3.366
3.399
V
V
Output Voltage
Output Voltage
4.5V < VIN < 32V, 0 < VCSH – VOUT < 75mV
VIN = 4.5V to 32V, VCSH – VOUT = 50mV
3.3
V
Output Voltage Line Regulation
Output Voltage Load Regulation
Output Voltage Total Regulation
MIC2182-5.0
0.03
0.5
0.8
%/V
%
25mV < (VCSH – VOUT) < 75mV (PWM mode only)
0mV < (V
– V
) < 75mV (full load range) 4.5V < V < 32V
%
CSH
OUT
IN
Output Voltage
4.95
4.90
4.85
5.0
5.0
5.05
5.10
V
V
Output Voltage
Output Voltage
6.5V < VIN < 32V, 0 < VCSH – VOUT < 75mV
VIN = 6.5V to 32V, VCSH – VOUT = 50mV
5.0
5.150
V
Output Voltage Line Regulation
Output Voltage Load Regulation
Output Voltage Total Regulation
Input and VDD Supply
PWM Mode
0.03
0.5
0.8
%/V
%
25mV < (VCSH – VOUT) < 75mV (PWM mode only)
0mV < (VCSH – VOUT) < 75mV (full load range) 6.5V < V < 32V
%
IN
VPWM = 0V, excluding external MOSFET gate drive current
IL = 0mA, VPWM floating (1nF capacitor to ground)
VEN/UVLO = 0V
1.6
600
0.1
2.5
1500
5
mA
µA
µA
V
Skip Mode
Shutdown Quiescent Current
Digital Supply Voltage (VDD
Undervoltage Lockout
)
IL = 0mA to 5mA
4.7
5.3
VDD upper threshold (turn on threshold)
VDD lower threshold (turn off threshold)
4.2
4.1
V
V
M9999-042204
4
April 22, 2004
MIC2182
Micrel
Parameter
Condition
Min
Typ
Max
Units
Reference Output (Fixed Versions Only)
Reference Voltage
1.220
1.245
1.270
V
Reference Line Regulation
Reference Load Regulation
Enable/UVLO
6V < VIN < 32V
1
2
mV
mV
0µA < IREF < 100µA
Enable Input Threshold
UVLO Threshold
0.6
2.2
1.1
2.5
0.1
1.6
2.8
5
V
V
Enable Input Current
Soft Start
VEN/UVLO = 5V
µA
Soft-Start Current
VSS = 0V
–3.5
–5
100
20
–6.5
µA
Current Limit
Current-Limit Threshold Voltage
Error Amplifier
VCSH = VOUT
75
135
mV
Error Sense Amplifier Gain
Current Amp
Current Sense Amplifier Gain
Oscillator Section
Oscillator Frequency
Maximum Duty Cycle
Minimum On-Time
2.0
270
300
86
330
kHz
%
VOUT = VOUT(nominal) + 200mV
140
1.3
0.1
250
1.9
5
ns
SYNC Threshold Level
SYNC Input Current
SYNC Minimum Pulse Width
SYNC Capture Range
Frequency Foldback Threshold
Foldback Frequency
Gate Drivers
0.7
V
VSYNC = 5V
µA
ns
200
330
0.75
Note 6
kHz
V
measured at VOUT pin
0.95
60
1.15
kHz
Rise/Fall Time
CL = 3000pF
60
ns
Output Driver Impedance
source
sink
5
3.5
8.5
6
Ω
Ω
Driver Nonoverlap Time
PWM Input
80
ns
PWM Input Current
VPWM = 0V
–10
µA
Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
Note 4. 25°C limits are 100% production tested. Limits over the operating temperature range are guaranteed by design and are not production tested.
Note 5. > 1.3 × V (for the feedback voltage reference and output voltage line and total regulation).
Note 6. See applications information for limitations on the maximum operating frequency.
V
IN
OUT
April 22, 2004
5
M9999-042204
MIC2182
Micrel
Typical Characteristics
Quiescent Current
vs. Temperature
Quiescent Current
vs. Supply Voltage
Quiescent Current
vs. Temperature
2.0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1.50
1.00
0.50
0
1.8
PWM
1.6
UVLO Mode
(mA)
1.4
1.2
1.0
0.8
-0.520
0.15
0.10
0.05
0
PWM
Skip
Skip
0.6
0.4
0.2
0
SHUTDOWN
(µA)
-40 -20
0 20 40 60 80 100120140
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100120140
0
0
0
0
4
8
12 16 20 24 28 32
TEMPERATURE (°C)
INPUT VOLTAGE (V)
V
(Fixed Versions)
V
(Fixed Versions)
REF
Load Regulation
Quiescent Current
vs. Supply Voltage
REF
Line Regulation
1.5
1.0
0.5
0
1.256
1.254
1.252
1.250
1.248
1.246
1.244
1.242
1.240
1.238
1.236
1.260
1.250
1.240
1.230
1.220
1.210
1.200
UVLO Mode
(mA)
0.5
0.4
0.3
0.2
0.1
0
-
SHUTDOWN
(µA)
0
4
8
12 16 20 24 28 32
0
4
8
12 16 20 24 28 32
200 400 600 800 1000
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
LOAD CURRENT (µA)
V
(Fixed Versions)
REF
V
V
DD
DD
vs. Temperature
Line Regulation
Load Regulation
1.260
1.255
1.250
1.245
1.240
5.0
4.8
4.6
4.4
4.2
4.0
5.00
4.95
4.90
4.85
4.80
-40 -20
0 20 40 60 80 100120140
0
4
8
12 16 20 24 28 32
5
10
15
20
25
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
LOAD CURRENT (mA)
V
Oscillator Frequency
vs. Supply Voltage
Oscillator Frequency
vs. Temperature
DD
vs. Temperature
10
8
1.0
0.8
0.6
0.4
0.2
0
4.98
4.96
4.94
4.92
4.90
4.88
4.86
4.84
4.82
6
4
2
0
-2
-4
-6
-8
-10
-0.2
-0.4
-0.6
-0.8
-1.0
-40 -20
0 20 40 60 80 100120140
4
8
12 16 20 24 28 32
-40 -20
0
20 40 60 80 100120140
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
M9999-042204
6
April 22, 2004
MIC2182
Micrel
Soft-Start Current
vs. Temperature
Overcurrent Threshold
vs. Temperature
Current-Limit
Foldback
5
4
3
2
1
0
5.0
0.12
0.11
0.10
0.09
0.08
4.8
4.6
4.4
4.2
4.0
VIN = 5V
OUT = 3.3V
CS = 15mΩ
V
R
0
1
2
3
4
5
6
7
8
-40 -20
0
20 40 60 80 100120140
-40 -20 0 20 40 60 80 100120140
OUTPUT CURRENT (A)
TEMPERATURE (°C)
TEMPERATURE (°C)
April 22, 2004
7
M9999-042204
MIC2182
Micrel
Block Diagrams
VIN
CIN
VDD
VIN
EN/UVLO
VDD
6
11
Reference
4.7µF
VIN
10
D2
SS
1
VBST
14
Control
Logic
HSD
CBST
L1
16
Q2
RCS
VOUT
COUT
PWM
VSW
15
2
LSD
13
D1
Q1
PGND
12
Current
Limit
PWM Mode
to Skip
Mode
0.024V
Skip-Mode
Current
Limit
0.07V
Low
Comp
–2%VBG
Hysteresis
Comp
Current
Sense
Amp
CSH
8
PWM
CORRECTIVE
RAMP
RESET
VOUT
9
AV = 2
R1
R2
SYNC
Oscillator
Error
Amp
5
FB
7
COMP
3
SGND
4
CCOMP
100k
R1
Gm = 0.2×10-3
V
= 1.245V 1+
= 6.0V
RCOMP
OUT
R2
MIC2182 [adj.]
V
OUT(max)
Figure 2a. Adjustable Output Voltage Version
M9999-042204
8
April 22, 2004
MIC2182
Micrel
VIN
CIN
VDD
VIN
EN/UVLO
VDD
6
11
Reference
4.7µF
VIN
10
D2
SS
1
VBST
14
Control
Logic
HSD
CBST
L1
16
Q2
RCS
VOUT
COUT
PWM
VSW
15
2
LSD
13
D1
Q1
PGND
12
Current
Limit
PWM Mode
to Skip
Mode
0.024V
Skip-Mode
Current
Limit
0.07V
Low
Comp
–2%VBG
Hysteresis
Comp
Current
Sense
Amp
CSH
8
PWM
CORRECTIVE
RAMP
RESET
VOUT
9
AV = 2
*82.5k for 3.3V Output
150k for 5V Output
SYNC
R1*
Oscillator
Error
Amp
5
SGND
4
COMP
R2
50k
3
VREF
7
CCOMP
100k
Gm = 0.2×10-3
RCOMP
MIC2182-x.x
Figure 2b. Fixed Output Voltage Versions
April 22, 2004
9
M9999-042204
MIC2182
Micrel
Control Loop
Functional Description
See “Applications Information” following this section for com-
ponent selection information and Figure 14 and Tables 1
through 5 for predesigned circuits.
PWM and Skip Modes of Operation
The MIC2182 operates in PWM (pulse-width-modulation)
mode at heavier output load conditions. At lighter load condi-
tions, the controller can be configured to automatically switch
to a pulse-skipping mode to improve efficiency. The potential
disadvantage of skip mode is the variable switching fre-
quency that accompanies this mode of operation. The occur-
rence of switching pulses depends on component values as
well as line and load conditions. There is an external sync
function that is disabled in skip mode. In PWM mode, the
synchronous buck converter forces continuous current to
flowintheinductor.Inskipmode,currentthroughtheinductor
can settle to zero, causing voltage ringing across the induc-
tor. Pulling the PWM pin (pin 2) low will force the controller to
operate in PWM mode for all load conditions, which will
improve cross regulation of transformer-coupled, multiple
output configurations.
The MIC2182 is a BiCMOS, switched-mode, synchronous
step-down (buck) converter controller. Current-mode control
is used to achieve superior transient line and load regulation.
An internal corrective ramp provides slope compensation for
stable operation above a 50% duty cycle. The controller is
optimized for high-efficiency, high-performance dc-dc con-
verter applications.
The MIC2182 block diagrams are shown in Figure 2a and
Figure 2b.
The MIC2182 controller is divided into 6 functions.
• Control loop
- PWM operation
- Skip-mode operation
PWM Control Loop
• Current limit
The MIC2182 uses current-mode control to regulate the
output voltage. This method senses the output voltage (outer
loop) and the inductor current (inner loop). It uses inductor
current and output voltage to determine the duty cycle of the
buck converter. Sampling the inductor current removes the
inductor from the control loop, which simplifies compensa-
tion.
• Reference, enable, and UVLO
• MOSFET gate drive
• Oscillator and sync
• Soft start
VIN
CIN
VDD
VIN
VDD
11
Reference
4.7µF
VIN
10
D2
VBST
14
CONTROL LOGIC AND
PULSE-WIDTH MODULATOR
HSD
CBST
16
Q2
Q1
L1
RCS
VOUT
COUT
VSW
15
LSD
13
D1
PWM Mode
to Skip
Mode
PGND
12
Q
LOW
FORCES
SKIP MODE
0.024V
R
S
Current
Sense
Amp
CSH
8
PWM
COMPARATOR
VOUT
9
CORRECTIVE
RAMP
RESET
AV = 2
R1
R2
Oscillator
Error
Amp
FB
7
COMP
3
R1
CCOMP
RCOMP
100k
V
= 1.245V 1+
OUT
Gm = 0.2×10-3
R2
MIC2182 [adj.] PWM Mode
Figure 3. PWM Operation
M9999-042204
10
April 22, 2004
MIC2182
Micrel
Skip-Mode Control Loop
A block diagram of the MIC2182 PWM current-mode control
loop is shown in Figure 3 and the PWM mode voltage and
current waveforms are shown in figure 5A. The inductor
current is sensed by measuring the voltage across the
This control method is used to improve efficiency at light
output loads. At light output currents, the power drawn by the
MIC2182 is equal to the input voltage times the IC supply
resistor, R . A ramp is added to the amplified current-sense
current (I ). At light output currents, the power dissipated by
CS
Q
signal to provide slope compensation, which is required to
prevent unstable operation at duty cycles greater than 50%.
the IC can be a significant portion of the total output power,
whichlowerstheefficiencyofthepowersupply.TheMIC2182
draws less supply current in skip mode by disabling portions
of the control and drive circuitry when the IC is not switching.
The disadvantage of this method is greater output voltage
ripple and variable switching frequency.
A transconductance amplifier is used for the error amplifier,
which compares an attenuated sample of the output voltage
with a reference voltage. The output of the error amplifier is
the COMP (compensation) pin, which is compared to the
current-sensewaveforminthePWMblock. Whenthecurrent
signal becomes greater than the error signal, the comparator
turns off the high-side drive. The COMP pin (pin 3) provides
access to the output of the error amplifier and allows the use
of external components to stabilize the voltage loop.
AblockdiagramoftheMIC2182skipmodeisshowninFigure
4. Skip mode voltage and current waveforms are shown in
figure 5B.
VIN
CIN
VDD
VDD
11
Reference
VIN
4.7µF
VIN
10
D2
VBST
14
CONTROL LOGIC AND
SKIP-MODE LOGIC
HSD
CBST
16
Q2
Q1
L1
RCS
VOUT
COUT
VSW
15
LOW-SIDE DRIVER
ONE SHOT
LSD
13
PGND
12
Q
R
S
Skip-Mode
Current
Limit
0.07V
Low
Comp
ONE SHOT
–2%VBG
LOW
FORCES
PWM MODE
Hysteresis
Comp
±1%
Current
Sense
Amp
CSH
8
VOUT
9
AV = 2
R1
R2
FB
7
R1
MIC2182 [adj.] Skip Mode
V
= 1.245V 1+
OUT
R2
Figure 4. Skip-Mode Operation
April 22, 2004
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M9999-042204
MIC2182
Micrel
VIN
0V
VSW
ILOAD
IL1
0A
VDD
Reset
Pulse
0V
VIN + VDD
VHSD
0V
VDD
0V
VLSD
Figure 5a. PWM-Mode Timing
VDD
VHSD
0V
VDD
VLSD
0V
VIN
VOUT
VSW
0V
ILIM(skip)
IL1
0A
VDD
Vone-shot
0V
+1%
VNOMINAL
VOUT
–1%
0V
IOUT
0A
Figure 5b. Skip-Mode Timing
A hysteretic comparator is used in place of the PWM error
amplifier and a current-limit comparator senses the inductor
current. A one-shot starts the switching cycle by momentarily
turning on the low side MOSFET to insure the high-side drive
boost capacitor, Cbst, is fully charged. The high-side MOS-
FET is turned on and current ramps up in the inductor, L1.
The high-side drive is turned off when either the peak voltage
on the input of the current-sense comparator exceeds the
threshold, typically 35mV, or the output voltage rises above
the hysteretic threshold of the output voltage comparator.
Once the high-side MOSFET is turned off, the load current
Figure 6 shows the improvement in efficiency that skip mode
makes when at lower output currents.
100
PWM
80
Skip
60
40
20
0
0.01
0.1
1
10
100
discharges the output capacitor, causing V
to fall. The
OUT
OUTPUT CURRENT (A)
cycle repeats when V
1%.
falls below the lower threshold, –
OUT
Figure 6. Efficiency
The maximum peak inductor current depends on the skip-
mode current-limit threshold and the value of the current-
sense resistor, R
.
CS
35mV
I
=
inductor(peak)
R
sense
M9999-042204
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April 22, 2004
MIC2182
Micrel
Switching from PWM to Skip Mode
rent-limit threshold is 100mV+35mV –25mV. The current-
sense resistor must be sized using the minimum current-limit
threshold. The external components must be designed to
withstand the maximum current limit. The current-sense
resistor value is calculated by the equation below:
The current sense amplifier in Figure 3 monitors the average
voltage across the current-sense resistor. The controller will
switch from PWM to skip mode when the average voltage
across the current-sense resistor drops below approximately
12mV.ThisisshowninFigure7b.Theaverageoutputcurrent
at this transition level for is calculated below.
75mV
RCS
=
IOUT(max)
0.012
I
=
The maximum output current is:
135mV
OUT(skipmode)
R
CS
IOUT(max)
=
where:
RCS
0.012 = threshold voltage of the internal comparator
= current-sense resistor value
The current-sense pins CSH (pin 8) and V
(pin 9) are
OUT
R
CS
noise sensitive due to the low signal level and high input
impedance.ThePCBtracesshouldbeshortandroutedclose
toeachother.Asmall(1nFto0.1µF)capacitoracrossthepins
will attenuate high frequency switching noise.
Switching from Skip to PWM Mode
The frequency of occurrence of the skip-mode current pulses
increase as the output current increases until the hysteretic
dutycyclereaches100%(continuouspulses). Increasingthe
current past this point will cause the output voltage will drop.
The low limit comparator senses the output voltage when it
drops below 2% of the set output and automatically switches
the converter to PWM mode.
When the peak inductor current exceeds the current-limit
threshold, the current-limit comparator, in Figure 2, turns off
the high-side MOSFET for the remainder of the cycle. The
output voltage drops as additional load current is pulled from
the converter. When the output voltage reaches approxi-
mately 0.95V, the circuit enters frequency-foldback mode
andtheoscillatorfrequencywilldropto60kHzwhilemaintain-
ing the peak inductor current equal to the nominal 100mV
across the external current-sense resistor. This limits the
maximum output power delivered to the load under a short
circuit condition.
The inductor current in skip mode is a triangular wave shape
a minimum value of 0 and a maximum value of 35mV/R
(seeFigure7b). Themaximumaverageoutputcurrentinskip
mode is the average value of the inductor waveform:
CS
35mV
I
= 0.5 ×
OUT(maxskipmode)
R
CS
Reference, Enable, and UVLO Circuits
The capacitor on the PWM pin (pin 2) is discharged when the
IC transitions from skip to PWM mode. This forces the IC to
remain in PWM mode for a fixed period of time. The added
delay prevents unwanted switching between PWM and skip
mode. The capacitor is charged with a 10uA current source
onpin2. Thethresholdonpin2is2.5V. Thedelayforatypical
1nF capacitor is:
The output drivers are enabled when the following conditions
are satisfied:
• The V voltage (pin 11) is greater than its
DD
undervoltage threshold (typically 4.2V).
• The voltage on the enable pin is greater than the
enable UVLO threshold (typically 2.5V)
The internal bias circuit generates a 1.245V bandgap refer-
C
× V
threshold
1nF × 2.5V
10µA
PWM
ence voltage for the voltage error amplifier and a 5V V
t
=
=
= 250µs
DD
delay
I
source
voltage for the gate drive circuit. The reference voltage in the
fixed-output-voltage versions of the MIC2182 is buffered and
where:
brought to pin 7. The V
pin should be bypassed to GND
REF
C
= capacitor connected to pin 2
PWM
(pin 4) with a 0.1µF capacitor. The adjustable version of the
MIC2182 uses pin 7 for output voltage sensing. A decoupling
capacitor on pin 7 is not used in the adjustable output voltage
version.
Current Limit
The current-limit circuit operates during PWM mode. The
output current is detected by the voltage drop across the
external current-sense resistor (R in Figure 2.). The cur-
CS
35mV THRESHOLD
ACROSS RCS
.
ILIM(skip)
Inductor
Current
0A
Figure 7a. Maximum Skip-Mode-Load Inductor Current
IMIN(PWM)
0A
12mV THRESHOLD
OF AVERAGE VOLTAGE
Inductor
Current
ACROSS RCS
.
Figure 7b. Minimum PWM-Mode-Load Inductor Current for PWM Operation
April 22, 2004
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M9999-042204
MIC2182
Micrel
The enable pin (pin 6) has two threshold levels, allowing the
MIC2182toshutdowninalowcurrentmode,orturnoffoutput
switching in UVLO mode. An enable pin voltage lower than
the shutdown threshold turns off all the internal circuitry and
reduces the input current to typically 0.1µA.
Oscillator and Sync
Theinternaloscillatorisfreerunningandrequiresnoexternal
components. The nominal oscillator frequency is 300kHz. If
the output voltage is below approximately 0.95V, the oscilla-
tor operates in a frequency-foldback mode and the switching
frequency is reduced to 60kHz.
If the enable pin voltage is between the shutdown and UVLO
thresholds, theinternalbias, V , andreferencevoltagesare
The SYNC input (pin 5) allows the MIC2182 to synchronize
with an external clock signal. The rising edge of the sync
signal generates a reset signal in the oscillator, which turns
off the low-side gate drive output. The high-side drive then
turns on, restarting the switching cycle. The sync signal is
inhibited when the controller operates in skip mode or during
frequency foldback. The sync signal frequency must be
greater than the maximum specified free running frequency
of the MIC2182. If the synchronizing frequency is lower,
double pulsing of the gate drive outputs will occur. When not
used, the sync pin must be connected to ground.
DD
turned on. The soft-start pin is forced low by an internal
discharge MOSFET. The output drivers are inhibited from
switching and remain in a low state. Raising the enable
voltage above the UVLO threshold of 2.5V allows the soft-
start capacitor to charge and enables the output drivers.
Either of two UVLO conditions will pull the soft-start capacitor
low.
• When the V drops below 4.1V
DD
• When the enable pin drops below the 2.5V
threshold
Figure 8 shows the timing between the external sync signal
(trace 2), the low-side drive (trace 1) and the high-side drive
(trace R1). There is a delay of approximately 250ns between
the rising edge of the external sync signal and turnoff of the
low-side MOSFET gate drive.
MOSFET Gate Drive
The MIC2182 high-side drive circuit is designed to switch an
N-channelMOSFET.ReferringtotheblockdiagraminFigure
2, a bootstrap circuit, consisting of D2 and C
energy to the high-side drive circuit. Capacitor C
charged while the low-side MOSFET is on and the voltage on
, supplies
BST
is
BST
Some concerns of operating at higher frequencies are:
• Higher power dissipation in the internal V
the V pin (pin 15) is approximately 0V. When the high-side
DD
SW
regulator. This occurs because the MOSFET
gates require charge to turn on the device. The
average current required by the MOSFET gate
increases with switching frequency. This in-
creases the power dissipated by the internal
MOSFETdriveristurnedon, energyfromC
isusedtoturn
BST
theMOSFETon. AstheMOSFETturnson, thevoltageonthe
pin increases to approximately V . Diode D2 is re-
V
SW
IN
versed biased and C
floats high while continuing to keep
BST
the high-side MOSFET on. When the low-side switch is
turned back on, C is recharged through D2.
V
regulator. Figure 10 shows the total gate
DD
BST
charge which can be driven by the MIC2182
over the input voltage range, for different values
of switching frequency. The total gate charge
includes both the high- and low-side MOSFETs.
The larger SOP package is capable of dissipat-
ing more power than the SSOP package and
can drive larger MOSFETs with higher gate
drive requirements.
The drive voltage is derived from the internal 5V V
bias
DD
supply. The nominal low-side gate drive voltage is 5V and the
nominal high-side gate drive voltage is approximately 4.5V
due the voltage drop across D2. A fixed 80ns delay between
the high- and low-side driver transitions is used to prevent
currentfromsimultaneouslyflowingunimpededthroughboth
MOSFETs.
TIME
Figure 8. Sync Waveforms
Figure 9. Startup Waveforms
M9999-042204
14
April 22, 2004
MIC2182
• Reduced maximum duty cycle due to switching
Micrel
Thesoft-startvoltageisapplieddirectlytothePWMcompara-
tor. A 5uA internal current source is used to charge up the
soft-start capacitor. The capacitor is discharged when either
the enable voltage drops below the UVLO threshold (2.5V) or
transition times and constant delay times in the
controller. As the switching frequency increased,
the switching period decreases. The switching
transition times and constant delays in the
MIC2182 start to become noticeable. The effect
is to reduce the maximum duty cycle of the
controller. This will cause the minimum input to
output differential voltage (dropout voltage) to
increase.
the V voltage drops below the UVLO level (4.1V).
DD
Thepartswitchesataminimumdutycyclewhenthesoft-start
pin voltage is less than 0.4V. This maintains a charge on the
bootstrap capacitor and insures high-side gate drive voltage.
As the soft-start voltage rises above 0.4V, the duty cycle
increases from the minimum duty cycle to the operating duty
cycle. The oscillator runs at the foldback frequency of 60kHz
until the output voltage rises above 0.95V. Above 0.95V, the
switching frequency increases to 300kHz (or the sync’d
frequency), causing the output voltage to rise a greater rate.
The rise time of the output is dependent on the soft-start
capacitor, output capacitance, output voltage, and load cur-
rent. The oscilloscope photo in Figure 9 show the output
voltage and the soft-start pin voltage at startup.
100
SOP
80
60
40
20
0
300kHz
400kHz
500kHz
Minimum Pulse Width
0
4
8
12 16 20 24 28 32
SUPPLY VOLTAGE (V)
The MIC2182 has a specified minimum pulse width. This
minimum pulse width places a lower limit on the minimum
duty cycle of the buck converter. When the MIC2182 is
operating in forced PWM mode (pin 2 low) and when the
output current is very low or zero, there is a limit on the ratio
Figure 10a. SOP Gate Charge vs. Input Voltage
100
SSOP
80
60
of V
/V . If this limit is exceeded, the output voltage will
OUT IN
rise above the regulated voltage level. A minimum load is
required to prevent the output from rising up. This will not
occur for output voltages greater than 3V.
300kHz
40
400kHz
20
Figure 11 should be used as a guide when the MIC2182 is
forced into PWM-only mode. The actual maximum input
voltage will depend on the exact external components used
(MOSFETs, inductors, etc.).
500kHz
0
0
4
8
12 16 20 24 28 32
SUPPLY VOLTAGE (V)
35
30
25
20
15
10
Figure 10b. SSOP Gate Charge vs. Input Voltage
It is recommended that the user limits the maximum synchro-
nized frequency to 600kHz. If a higher synchronized fre-
quency is required, it may be possible and will be design
dependent. Please consult Micrel applications for assis-
tance.
Soft Start
Soft start reduces the power supply input surge current at
startup by controlling the output voltage rise time. The input
surge appears while the output capacitance is charged up. A
slower output rise time will draw a lower input surge current.
Soft start may also be used for power supply sequencing.
0
1
2
3
4
5
6
OUTPUT VOLTAGE (V)
Figure 11. Max. Input Voltage in Forced-PWM Mode
This restriction does not occur when the MIC2182 is set to
automatic mode (pin 2 connected to a capacitor) since the
converter operates in skip mode at low output current.
April 22, 2004
15
M9999-042204
MIC2182
Micrel
output currents, the core losses can be a significant contribu-
tor. Core loss information is usually available from the mag-
netics vendor.
Applications Information
The following applications information includes component
selection and design guidelines. See Figure 14 and Tables 1
through 5 for predesigned circuits.
Copper loss in the inductor is calculated by the equation
below:
Inductor Selection
P
= Iinductor(rms)2 ×Rwinding
Values for inductance, peak, and RMS currents are required
to select the output inductor. The input and output voltages
andtheinductancevaluedeterminethepeaktopeakinductor
ripple current. Generally, higher inductance values are used
withhigherinputvoltages.Largerpeaktopeakripplecurrents
will increase the power dissipation in the inductor and
MOSFETs. Larger output ripple currents will also require
more output capacitance to smooth out the larger ripple
current. Smaller peak to peak ripple currents require a larger
inductance value and therefore a larger and more expensive
inductor. A good compromise between size, loss and cost is
to set the inductor ripple current to be equal to 20% of the
maximum output current.
inductorCu
The resistance of the copper wire, R
, increases with
winding
temperature.Thevalueofthewindingresistanceusedshould
be at the operating temperature.
R
= R
× 1+ 0.0042 ×(T − T
)
)
(
winding(hot)
winding(20°C)
hot
20°C
where:
T
= temperature of the wire
HOT
under operating load
T
= ambient temperature
20°C
R
is room temperature winding resistance
winding(20°C)
The inductance value is calculated by the equation below.
(usually specified by the manufacturer)
Current-Sense Resistor Selection
V
×(V
− V
)
OUT
IN(max)
OUT
L =
Low inductance power resistors, such as metal film resistors
should be used. Most resistor manufacturers make low
inductance resistors with low temperature coefficients, de-
signedspecificallyforcurrent-senseapplications. Bothresis-
tance and power dissipation must be calculated before the
V
× f × 0.2 ×I
S OUT(max)
IN(max)
where:
f = switching frequency
S
0.2 = ratio of ac ripple current to dc output current
= maximum input voltage
resistor is selected. The value of R
is chosen based on
SENSE
V
IN(max)
the maximum output current and the maximum threshold
level. The power dissipated is based on the maximum peak
output current at the minimum overcurrent threshold limit.
The peak-to-peak inductor current (ac ripple current) is:
VOUT ×(VIN(max) − VOUT
)
IPP
=
75mV
V
IN(max) × fS ×L
R
=
SENSE
I
OUT(max)
The peak inductor current is equal to the average output
current plus one half of the peak to peak inductor ripple
current.
The maximum overcurrent threshold is:
135mV
Iovercurrent(max)
=
IPK = IOUT(max) + 0.5 ×IPP
RCS
2
The RMS inductor current is used to calculate the I ·R losses
The maximum power dissipated in the sense resistor is:
in the inductor.
2
P
= I
×R
CS
D(RSENSE
)
overcurrent(max)
2
IPP
1
3 IOUT(max)
MOSFET Selection
Iinductor(rms) = IOUT(max) × 1+
External N-channel logic-level power MOSFETs must be
used for the high- and low-side switches. The MOSFET gate-
to-source drive voltage of the MIC2182 is regulated by an
Maximizing efficiency requires the proper selection of core
material and minimizing the winding resistance. The high
frequencyoperationoftheMIC2182requirestheuseofferrite
materials for all but the most cost sensitive applications.
Lower cost iron powder cores may be used but the increase
incorelosswillreducetheefficiencyofthepowersupply.This
is especially noticeable at low output power. The winding
resistance decreases efficiency at the higher output current
levels. The winding resistance must be minimized although
this usually comes at the expense of a larger inductor.
internal 5V V
operation is specified at V = 4.5V must be used.
regulator. Logic-level MOSFETs, whose
DD
GS
It is important to note the on-resistance of a MOSFET
increases with increasing temperature. A 75°C rise in junc-
tion temperature will increase the channel resistance of the
MOSFET by 50% to 75% of the resistance specified at 25°C.
This change in resistance must be accounted for when
calculating MOSFET power dissipation.
Total gate charge is the charge required to turn the MOSFET
on and off under specified operating conditions (V
Thepowerdissipatedintheinductorisequaltothesumofthe
core and copper losses. At higher output loads, the core
losses are usually insignificant and can be ignored. At lower
and
DS
V
). The gate charge is supplied by the MIC2182 gate drive
GS
circuit. At 300kHz switching frequency and above, the gate
M9999-042204
16 April 22, 2004
MIC2182
Micrel
charge can be a significant source of power dissipation in the
MIC2182. At low output load this power dissipation is notice-
able as a reduction in efficiency. The average current re-
quired to drive the high-side MOSFET is:
C
× V + C
× V
OSS
IN
ISS
GS
t
=
T
I
G
where:
C
and C
are measured at V = 0.
OSS DS
IG[high-side](avg) = QG × fS
ISS
I = gate drive current (1A for the MIC2182)
G
where:
The total high-side MOSFET switching loss is:
I
=
G[high-side](avg)
average high-side MOSFET gate current
P
= (V +V )×I × t × f
AC S
IN D PK T
Q = total gate charge for the high-side MOSFET
where:
G
taken from manufacturer’s data sheet
t = switching transition time
T
with V = 5V.
GS
(typically 20ns to 50ns)
The low-side MOSFET is turned on and off at V
= 0
DS
V = freewheeling diode drop, typically 0.5V.
D
because the freewheeling diode is conducting during this
time. The switching losses for the low-side MOSFET is
usually negligable. Also, the gate drive current for the low-
f it the switching frequency, nominally 300kHz
S
The low-side MOSFET switching losses are negligible and
can be ignored for these calculations.
side MOSFET is more accurately calculated using C
at
ISS
V
= 0 instead of gate charge.
RMS Current and MOSFET Power Dissipation Calculation
DS
For the low-side MOSFET:
= C
Under normal operation, the high-side MOSFET’s RMS
currentisgreatestwhenV islow(maximumdutycycle).The
IN
I
× V × f
GS S
G[low-side](avg)
ISS
low-sideMOSFET’sRMScurrentisgreatestwhenV ishigh
IN
Since the current from the gate drive comes from the input
voltage, the power dissipated in the MIC2182 due to gate
drive is:
(minimum duty cycle). However, the maximum stress the
MOSFETs see occurs during short circuit conditions, where
the output current is equal to I
. (See the Sense
overcurrent(max)
Resistor section). The calculations below are for normal
operation. To calculate the stress under short circuit condi-
P
= V
I
+I
G[low-side](avg)
(
)
gatedrive
IN G[high-side](avg)
tions, substituteI
forI
. Usetheformula
overcurrent(max)
OUT(max)
AconvenientfigureofmeritforswitchingMOSFETsistheon-
resistance times the total gate charge (R
below to calculate D under short circuit conditions.
× Q ). Lower
DS(on)
G
Dshortcircuit = 0.063 −1.8 ×10−3 × V
numbers translate into higher efficiency. Low gate-charge
logic-level MOSFETs are a good choice for use with the
MIC2182. Power dissipation in the MIC2182 package limits
the maximum gate drive current. Refer to Figure 10 for the
MIC2182 gate drive limits.
IN
The RMS value of the high-side switch current is:
2
IPP
2
ISW(highside)(rms) = D × IOUT(max)
+
12
Parameters that are important to MOSFET switch selection
are:
2
• Voltage rating
• On-resistance
• Total gate charge
I
2
PP
I
(rms) = 1−D I
+
(
)
SW(lowside)
OUT(max)
12
where:
The voltage rating of the MOSFETs are essentially equal to
the input voltage. A safety factor of 20% should be added to
D = duty cycle of the converter
the V
of the MOSFETs to account for voltage spikes
DS(max)
V
OUT
due to circuit parasitics.
D =
η × V
IN
The power dissipated in the switching transistor is the sum of
η = efficiency of the converter.
theconductionlossesduringtheon-time(P
)andthe
conduction
switchinglossesthatoccurduringtheperiodoftimewhenthe
Converter efficiency depends on component parameters,
which have not yet been selected. For design purposes, an
MOSFETs turn on and off (P ).
AC
efficiency of 90% can be used for V less than 10V and 85%
P
= P
+P
IN
SW
conduction
AC
can be used for V greater than 10V. The efficiency can be
IN
where:
Pconduction = ISW(rms)2 ×RSW
= P +P
moreaccuratelycalculatedoncethedesigniscomplete.Ifthe
assumed efficiency is grossly inaccurate, a second iteration
through the design procedure can be made.
P
For the high-side switch, the maximum dc power dissipation
is:
AC
AC(off)
AC(on)
R
= on-resistance of the MOSFET switch.
SW
2
Making the assumption the turn-on and turnoff transition
times are equal, the transition time can be approximated by:
P
= R
×I
(rms)
switch1(dc)
DS(on)1 SW1
April 22, 2004
17
M9999-042204
MIC2182
Micrel
For the low-side switch (N-channel MOSFET), the dc power
dissipation is:
circuit inductance will cause ringing during the high-side
MOSFET turn-on.
An external Schottky diode conducts at a lower forward
voltage preventing the body diode in the MOSFET from
turning on. The lower forward voltage drop dissipates less
power than the body diode. The lack of a reverse recovery
mechanism in a Schottky diode causes less ringing and less
power loss. Depending on the circuit components and oper-
ating conditions, an external Schottky diode will give a 1/2%
to 1% improvement in efficiency. Figure 12 illustrates the
difference in noise on the VSW pin with and without a
Schottky diode.
2
P
= R
×I
(rms)
switch2(dc)
DS(on)2
SW2
Since the ac switching losses for the low side MOSFET is
near zero, the total power dissipation is:
P
= P
switch2(dc)
low-side MOSFET(max)
The total power dissipation for the high-side MOSFET is:
= P +P
P
highsideMOSFET(max)
SWITCH 1(dc)
AC
External Schottky Diode
Output Capacitor Selection
An external freewheeling diode is used to keep the inductor
current flow continuous while both MOSFETs are turned off.
This dead time prevents current from flowing unimpeded
through both MOSFETs and is typically 80ns The diode
conducts twice during each switching cycle. Although the
averagecurrentthroughthisdiodeissmall, thediodemustbe
able to handle the peak current.
The output capacitor values are usually determined by the
capacitorsESR(equivalentseriesresistance).Voltagerating
and RMS current capability are two other important factors in
selectingtheoutputcapacitor.Recommendedcapacitorsare
tantalum, low-ESR aluminum electrolytics, and OS-CON.
The output capacitor’s ESR is usually the main cause of
output ripple. The maximum value of ESR is calculated by:
ID(avg) = IOUT × 2 × 80ns × fS
∆V
OUT
The reverse voltage requirement of the diode is:
R
≤
ESR
I
PP
V
(rrm) = V
IN
diode
where:
The power dissipated by the Schottky diode is:
V
I
= peak to peak output voltage ripple
OUT
Pdiode = ID(avg) × VF
= peak to peak inductor ripple current
PP
where:
The total output ripple is a combination of the ESR and the
output capacitance. The total ripple is calculated below:
V = forward voltage at the peak diode current
F
The external Schottky diode, D2, is not necessary for circuit
operation since the low-side MOSFET contains a parasitic
body diode. The external diode will improve efficiency and
decrease high frequency noise. If the MOSFET body diode is
used,itmustberatedtohandlethepeakandaveragecurrent.
The body diode has a relatively slow reverse recovery time
and a relatively high forward voltage drop. The power lost in
the diode is proportional to the forward voltage drop of the
diode. As the high-side MOSFET starts to turn on, the body
diodebecomesashortcircuitforthereverserecoveryperiod,
dissipating additional power. The diode recovery and the
2
I
PP ×(1−D)
2
∆VOUT
=
+ IPP ×RESR
(
)
COUT × fS
where:
D = duty cycle
= output capacitance value
C
OUT
f = switching frequency
S
The voltage rating of capacitor should be twice the output
voltage for a tantalum and 20% greater for an aluminum
electrolytic or OS-CON.
The output capacitor RMS current is calculated below:
I
PP
I
(rms) =
COUT
12
The power dissipated in the output capacitor is:
2
P
= I
(rms) ×R
DISS(COUT
)
COUT
ESR(COUT
)
Input Capacitor Selection
The input capacitor should be selected for ripple current
rating and voltage rating. Tantalum input capacitors may fail
whensubjectedtohighinrushcurrents,causedbyturningthe
input supply on. Tantalum input capacitor voltage rating
should be at least 2 times the maximum input voltage to
maximize reliability. Aluminum electrolytic, OS-CON, and
multilayer polymer film capacitors can handle the higher
inrush currents without voltage derating.
Figure 12. Switch Output Noise
With and Without Shottky Diode
M9999-042204
18
April 22, 2004
MIC2182
Micrel
The input voltage ripple will primarily depend on the input
capacitors ESR. The peak input current is equal to the peak
inductor current, so:
• Supply current to the MIC2182
• MOSFET gate-charge power (included in the IC
supply current)
∆V = I
×R
ESR(CIN
• Core losses in the output inductor
IN
inductor(peak)
)
To maximize efficiency at light loads:
The input capacitor must be rated for the input current ripple.
TheRMSvalueofinputcapacitorcurrentisdeterminedatthe
maximum output current. Assuming the peak to peak induc-
tor ripple current is low:
• Use a low gate-charge MOSFET or use the
smallest MOSFET, which is still adequate for
maximum output current.
• Allow the MIC2182 to run in skip mode at lower
IC (rms) ≈ IOUT(max)
×
D ×(1−D)
currents.
IN
• Use a ferrite material for the inductor core, which
has less core loss than an MPP or iron power
core.
The power dissipated in the input capacitor is:
2
P
= I (rms) ×R
DISS(CIN
)
CIN
ESR(CIN
)
Under heavy output loads the significant contributors to
power loss are (in approximate order of magnitude):
Voltage Setting Components
The MIC2182-3.3 and MIC2182-5.0 ICs contain internal
voltage dividers that set the output voltage. The MIC2182
adjustable version requires two resistors to set the output
voltage as shown in Figure 13.
• Resistive on-time losses in the MOSFETs
• Switching transition losses in the MOSFETs
• Inductor resistive losses
• Current-sense resistor losses
R1
• Input capacitor resistive losses (due to the
Error
Amp
FB
7
capacitors ESR)
R2
To minimize power loss under heavy loads:
• Use logic-level, low on-resistance MOSFETs.
Multiplying the gate charge by the on-resistance
gives a Figure of merit, providing a good bal-
ance between low and high load efficiency.
VREF
1.245V
MIC2182 [adj.]
Figure 13. Voltage-Divider Configuration
• Slow transition times and oscillations on the
voltage and current waveforms dissipate more
power during turn-on and turnoff of the
MOSFETs. A clean layout will minimize parasitic
inductance and capacitance in the gate drive
and high current paths. This will allow the fastest
transition times and waveforms without oscilla-
tions. Low gate-charge MOSFETs will transition
faster than those with higher gate-charge
requirements.
The output voltage is determined by the equation:
R1
VO = VREF × 1+
R2
Where: V
for the MIC2182 is typically 1.245V.
REF
A typical value of R1 can be between 3k and 10k. If R1 is too
large it may allow noise to be introduced into the voltage
feedback loop. If R1 is too small in value it will decrease the
efficiency of the power supply, especially at low output loads.
• For the same size inductor, a lower value will
have fewer turns and therefore, lower winding
resistance. However, using too small of a value
will require more output capacitors to filter the
output ripple, which will force a smaller band-
width, slower transient response and possible
instability under certain conditions.
Once R1 is selected, R2 can be calculated using:
V
×R1
REF
R2 =
V − V
O
REF
Voltage Divider Power Dissipation
The reference voltage and R2 set the current through the
voltage divider.
• Lowering the current-sense resistor value will
decrease the power dissipated in the resistor.
However, it will also increase the overcurrent
limit and will require larger MOSFETs and
inductor components.
VREF
Idivider
=
R2
The power dissipated by the divider resistors is:
• Use low-ESR input capacitors to minimize the
2
Pdivider = (R1+R2)×Idivider
power dissipated in the capacitors ESR.
Efficiency Calculation and Considerations
Decoupling Capacitor Selection
Efficiency is the ratio of output power to input power. The
difference is dissipated as heat in the buck converter. Under
light output load, the significant contributors are:
The 4.7µF decoupling capacitor is used to minimize noise on
the VDD pin. The placement of this capacitor is critical to the
proper operation of the IC. It must be placed right next to the
April 22, 2004
19
M9999-042204
MIC2182
Micrel
• When the high-side MOSFET is switched on, the
pins and routed with a wide trace. The capacitor should be a
good quality tantalum. An additional 1µF ceramic capacitor
may be necessary when driving large MOSFETs with high
gatecapacitance. IncorrectplacementoftheV decoupling
capacitor will cause jitter or oscillations in the switching
waveform and large variations in the overcurrent limit.
critical flow of current is from the input capacitor
through the MOSFET, inductor, sense resistor,
output capacitor, and back to the input capacitor.
These paths must be made with short, wide
pieces of trace. It is good practice to locate the
ground terminals of the input and output capaci-
tors close to each.
DD
A 0.1µF ceramic capacitor is required to decouple the VIN.
The capacitor should be placed near the IC and connected
directly to between pin 10 (Vcc) and pin 12 (PGND).
• When the low-side MOSFET is switched on,
current flows through the inductor, sense
resistor, output capacitor, and MOSFET. The
source of the low-side MOSFET should be
located close to the output capacitor.
PCB Layout and Checklist
PCB layout is critical to achieve reliable, stable and efficient
performance. A ground plane is required to control EMI and
minimize the inductance in power, signal and return paths.
• The freewheeling diode, D1 in Figure 2, con-
ducts current during the dead time, when both
MOSFETs are off. The anode of the diode
should be located close to the output capacitor
ground terminal and the cathode should be
located close to the input side of the inductor.
The following guidelines should be followed to insure proper
operation of the circuit.
• Signal and power grounds should be kept
separate and connected at only one location.
Large currents or high di/dt signals that occur
when the MOSFETs turn on and off must be
kept away from the small signal connections.
• The 4.7µF capacitor, which connects to the VDD
terminal (pin 11) must be located right at the IC.
The VDD terminal is very noise sensitive and
placement of this capacitor is very critical.
Connections must be made with wide trace. The
capacitor may be located on the bottom layer of
the board and connected to the IC with multiple
vias.
• The connection between the current-sense
resistor and the MIC2182 current-sense inputs
(pin 8 and 9) should have separate traces,
routed from the terminals directly to the IC pins.
The traces should be routed as closely as
possible to each other and their length should be
minimized. Avoid running the traces under the
inductor and other switching components. A 1nF
to 0.1µF capacitor placed between pins 8 and 9
will help attenuate switching noise on the current
sense traces. This capacitor should be placed
close to pins 8 and 9.
• The V bypass capacitor should be located
IN
close to the IC and connected between pins 10
and 12. Connections should be made with a
ground and power plane or with short, wide
trace.
M9999-042204
20
April 22, 2004
MIC2182
Micrel
Predesigned Circuits
Power supplies larger than 10A can also be constructed
using the MIC2182 using larger power-handling compo-
nents.
Asingleschematicdiagram,showninFigure 14,canbeused
tobuildpowersuppliesrangingfrom3Ato10Aatthecommon
outputvoltagesof1.8V,2.5V,3.3V,and5V.Componentsthat
vary, depending upon output current and voltage, are listed
in the accompanying Tables 3 through 6.
The“PowerSupplyOperatingCharacteristics”graphsfollow-
ing the component and vendor tables provide useful informa-
tion about the actual performance of some of these circuits.
D2
MIC2182
VDD
BST
EN/UVLO HSD
C11
VIN
SD103BWS
(table)
VIN
C9
4.7µF
16V
C5
0.1µF
R7
100k
C6
0.1µF
Q2
L1
(table)
R2
(table)
(table)
VOUT
PWM
VSW
LSD
C4
1nF
Q1
(table)
D1
(table)
C7
(table)
C12
0.1µF
50V
SS
PGND
CSH
GND
COMP
SYNC
C13, 1nF
R1
2k
C3
0.1µF
VOUT
VREF
C2
2.2nF
C1
0.1µF
50V
SGND
GND
Figure 14. Basic Circuit Diagram for Use with Tables 3 through 6
Specification
Switching frequency ripple
Maximum ambient temperature
Short-circuit capability
Limit
1% of output voltage
85°C
Continuous
300kHz
Switching frequency
Table 1. Specifications for Figure 14 and Tables 3 through 6
Manufacturer
AVX
Telephone Number (USA)
(803) 946-0690
(516) 435-1110
(561) 241-7876
(704) 264-8861
(310) 322-3331
(408) 944-0800
(805) 446-4800
Web Address
www.avxcorp.com
Central Semiconductor
www.centralsemi.com
www.coiltronics.com
Coiltronics
IRC
IR
www.irf.com
www.micrel.com
Micrel
Vishay/Lite On
(diodes)
www.vishay-liteon.com
Vishay/Siliconix
(MOSFETs)
(800) 554-5665
(800) 487-9437
www.siliconix.com
Vishay/Dale
www.vishaytechno.com
(inductors and resistors)
Sumida
(847) 956-0666
www.japanlink.com/sumida
Table 2. Component Suppliers
April 22, 2004
21
M9999-042204
MIC2182
Micrel
3A (6.5V–30V)
4A (6.5V–30V)
5A (6.5V–30V)
10A (6.5V–10V)
Reference
Part No. / Description
Part No. / Description
Part No. / Description
Part No. / Description
C7
qty: 2
qty: 2
qty: 2
qty: 2
TPSE227M010R0100
AVX, 220µF 10V,
0.1Ω ESR,
TPSE227M010R0100
AVX, 220µF 10V,
0.1Ω ESR,
TPSV227M010R0060
AVX, 220µF 10V,
0.06Ω ESR,
TPSV337M010R0060
AVX, 330µF 10V,
0.06Ω ESR,
output filter capacitor
output filter capacitor
output filter capacitor
output filter capacitor
C11
qty: 2
qty: 3
qty: 4
qty: 4
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSV107M020R0085
AVX, 100µF 20V,
0.06Ω ESR,
input filter capacitor
input filter capacitor
input filter capacitor
input filter capacitor
D1
L1
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B330, Vishay,
freewheeling diode
qty: 1 CDRH125-100,
Sumida Inductor,
10µH 4A,
qty: 1 CDRH127-100,
Sumida Inductor,
10µH 5A,
qty: 1 CDRH127-100
Sumida,
10µH 5A,
qty: 1 UP4B-3R3,
Coiltronics,
3.3µH 11A,
output inductor
output inductor
output inductor
output inductor
Q1
Q2
R2
qty: 1 Si4800, Siliconix,
low-side MOSFET
qty: 1 Si4800, Siliconix,
low-side MOSFET
qty: 1 Si4884, Siliconix,
low-side MOSFET
qty: 2 Si4884, Siliconix
low-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 1 Si4884, Siliconix,
high-side MOSFET
qty: 2 Si4884, Siliconix,
high-side MOSFET
qty: 1
qty: 1
qty: 1
qty: 2
WSL-2010 .025 1%,
Vishay, 0.025, 1%, 0.5W,
current sense resistor
WSL-2010 .020 1%,
Vishay, 0.02, 1%, 0.5W,
current sense resistor
WSL-2512 .015 1%,
Vishay, 0.015, 1%, 1W,
current sense resistor
WSL-2512 .015 1% ,
Vishay, 0.015, 1%, 1W,
current sense resistor
U1
MIC2182-5.0BSM or
MIC2182-5.0BM
MIC2182-5.0BSM or
MIC2182-5.0BM
MIC2182-5.0BSM or
MIC2182-5.0BM
MIC2182-5.0BM
Table 3. Components for 5V Output
3A (4.5V–30V)
4A (4.5V–30V)
5A (4.5V–30V)
10A (4.5V–5.5V)
Reference
C7
Part No. / Description
Part No. / Description
Part No. / Description
Part No. / Description
qty: 2
qty: 2
qty: 2
qty: 2
TPSE227M010R0100
AVX, 220µF 10V,
0.1Ω ESR,
TPSE227M010R0100
AVX, 220µF 10V,
0.1Ω ESR,
TPSV227M010R0060
AVX, 220µF 10V,
0.06Ω ESR,
TPSV477M006R0055
AVX, 470µF 6.3V,
0.055Ω ESR,
output filter capacitor
output filter capacitor
output filter capacitor
output filter capacitor
C11
qty: 2
qty: 2
qty: 3
qty: 3
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSV227M016R0075
AVX, 220µF 16V,
0.075Ω ESR,
filter capacitor
input filter capacitor
input filter capacitor
input filter capacitor
D1
L1
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B330, Vishay,
freewheeling diode
qty: 1 CDRH125-100,
Sumida Inductor,
10µH 4A,
qty: 1 CDRH127-100,
Sumida Inductor,
10µH 5A,
qty: 1 CDRH127-100
Sumida,
10µH 5A,
qty: 1 UP4B-3R3,
Coiltronics,
3.3µH 11A,
output inductor
output inductor
output inductor
output inductor
Q1
Q2
R2
qty: 1 Si4800, Siliconix,
low-side MOSFET
qty: 1 Si4800, Siliconix,
low-side MOSFET
qty: 1 Si4800, Siliconix,
low-side MOSFET
qty: 2 Si4884, Siliconix,
low-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 1 Si4884, Siliconix,
high-side MOSFET
qty: 2 Si4884, Siliconix,
high-side MOSFET
qty: 1
qty: 1
qty: 1
qty: 2
WSL-2010 .025 1%,
Vishay, 0.025, 1%, 0.5W,
current sense resistor
WSL-2010 .020 1%,
Vishay, 0.02, 1%, 0.5W,
current sense resistor
WSL-2512 .015 1%,
Vishay, 0.015, 1%, 1W,
current sense resistor
WSL-2512 .015 1% ,
Vishay, 0.015, 1%, 1W,
current sense resistor
U1
MIC2182-3.3BSM or
MIC2182-3.3BM
MIC2182-3.3BM or
MIC2182-3.3BSM
MIC2182-3.3BM or
MIC2182-3.3BSM
MIC2182-3.3BM
Table 4. Components for 3.3V Output
M9999-042204
22
April 22, 2004
MIC2182
Micrel
3A (4.5V–30V)
4A (4.5V–30V)
5A (4.5V–30V)
10A (4.5V–5.5V)
Reference
Part No. / Description
Part No. / Description
Part No. / Description
Part No. / Description
C7
qty: 2
qty: 2
qty: 2
qty: 2
TPSE227M010R0100
AVX, 220µF 10V,
0.1Ω ESR,
TPSE227M010R0100
AVX, 220µF 10V,
0.1Ω ESR,
TPSV227M010R0060
AVX, 220µF 10V,
0.06Ω ESR,
TPSV447M006R0055
AVX, 470µF 6.3V,
0.06Ω ESR,
output filter capacitor
output filter capacitor
output filter capacitor
output filter capacitor
C11
qty: 2
qty: 2
qty: 2
qty: 3
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSV227M016R0075
AVX, 220µF 16V,
0.06Ω ESR,
input filter capacitor
input filter capacitor
input filter capacitor
input filter capacitor
D1
L1
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B330, Vishay,
freewheeling diode
qty: 1 CDRH125-100,
Sumida Inductor,
10µH 4A,
qty: 1 CDRH127-100,
Sumida Inductor,
10µH 5A,
qty: 1 CDRH127-100
Sumida,
10µH 5A,
qty: 1 UP4B-3R3,
Coiltronics,
3.3µH 11A,
output inductor
output inductor
output inductor
output inductor
Q1
Q2
R2
qty: 1 Si4800, Siliconix,
low-side MOSFET
qty: 1 Si4884, Siliconix,
low-side MOSFET
qty: 1 Si4884, Siliconix,
low-side MOSFET
qty: 2 Si4884, Siliconix
low-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 2 Si4884, Siliconix,
high-side MOSFET
qty: 1
qty: 1
qty: 1
qty: 1
WSL-2010 .025 1%,
Vishay, 0.025, 1%, 0.5W,
current sense resistor
WSL-2010 .020 1%,
Vishay, 0.02, 1%, 0.5W,
current sense resistor
WSL-2512 .015 1%,
Vishay, 0.015, 1%, 1W,
current sense resistor
WSL-2512 .015 1% ,
Vishay, 0.015, 1%, 1W,
current sense resistor
U1
MIC2182BSM or
MIC2182BSM or
MIC2182BSM or
MIC2182BM
MIC2182BM
MIC2182BM
MIC2182BM
Table 5. Components for 2.5V Output
3A (4.5V–30V)
4A (4.5V–30V)
5A (4.5V–8V)
10A (4.5V–5.5V)
Reference
Part No. / Description
Part No. / Description
Part No. / Description
Part No. / Description
C7
qty: 2
qty: 2
qty: 2
qty: 2
TPSE227M010R0100
AVX, 220µF 10V,
0.1Ω ESR,
TPSE227M010R0100
AVX, 220µF 10V,
0.1Ω ESR,
TPSV227M010R0060
AVX, 220µF 10V,
0.06Ω ESR,
TPSV447M006R0055
AVX, 470µF 6.3V,
0.06Ω ESR,
output filter capacitor
output filter capacitor
output filter capacitor
output filter capacitor
C11
qty: 2
qty: 2
qty: 2
qty: 2
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSE226M035R0300
AVX, 22µF 35V,
0.3Ω ESR,
TPSV227M016R0075
AVX, 220µF 16V,
0.06Ω ESR,
input filter capacitor
input filter capacitor
input filter capacitor
input filter capacitor
D1
L1
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B140, Vishay,
freewheeling diode
qty: 1 B330, Vishay,
freewheeling diode
qty: 1 CDRH125-100,
Sumida Inductor,
10µH 4A,
qty: 1 CDRH127-100,
Sumida Inductor,
10µH 5A,
qty: 1 CDRH127-100
Sumida,
10µH 5A,
qty: 1 UP4B-3R3,
Coiltronics,
3.3µH 11A,
output inductor
output inductor
output inductor
output inductor
Q1
Q2
R2
qty: 1 Si4800, Siliconix,
low-side MOSFET
qty: 1 Si4884, Siliconix,
low-side MOSFET
qty: 1 Si4884, Siliconix,
low-side MOSFET
qty: 2 Si4884, Siliconix
low-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 1 Si4800, Siliconix,
high-side MOSFET
qty: 2 Si4884, Siliconix,
high-side MOSFET
qty: 1
qty: 1
qty: 1
qty: 2
WSL-2010 .025 1%,
Vishay, 0.025, 1%, 0.5W,
current sense resistor
WSL-2010 .020 1%,
Vishay, 0.02, 1%, 0.5W,
current sense resistor
WSL-2512 .015 1%,
Vishay, 0.015, 1%, 1W,
current sense resistor
WSL-2512 .015 1% ,
Vishay, 0.015, 1%, 1W,
current sense resistor
U1
MIC2182BSM or
MIC2182BSM or
MIC2182BSM or
MIC2182BM
MIC2182BM
MIC2182BM
MIC2182BM
Table 6. Components for 1.8V Output
April 22, 2004
23
M9999-042204
MIC2182
Micrel
Power Supply Operating Characteristics
Effect of Soft-Start Capacitor (CSS) Value
On Output Voltage Waveforms
During Turn-On
Effect of Soft-Start Capacitor (CSS) Value
On Output Voltage Waveforms
During Turn-On
(10A Power Supply Configuration)
(4A Power Supply Configuration)
Normal (300kHz Switching Frequency) and
Output Short-Circuit (60kHz) Conditions
Switch Node (Pin 15) Waveforms
Converter Waveforms
VIN = 7V
SWITCH-NODE
VOLTAGE
L1 = 3.3µH
VOUT = 3.3V
IOUT = 10A
HIGH-SIDE
DRIVE VOLTAGE
REFERENCED TO GROUND
QTY: 2
Si4884
HIGH-SIDE MOSFET
GATE-TO-SOURCE VOLTAGE
HIGH-SIDE
MOSFETS
QTY: 2
Si4884
LOW-SIDE
MOSFETS
LOW-SIDE MOSFET
GATE-TO-SOURCE VOLTAGE
10Amps
INDUCTOR CURRENT
Typical Skip-Mode Waveforms
Typical PWM-Mode Waveforms
M9999-042204
24
April 22, 2004
MIC2182
Micrel
Load Transient Response
and Bode Plot
Load Transient Response
and Bode Plot
(4A Power Supply Configuration)
(10A Power Supply Configuration)
V
IN = 12V
V
IN = 6V
VOUT = 3.3V
L1 = 10µH
R2 = 20mΩ
VOUT = 3.3V
L1 = 3.3µH
R2 = 7.5mΩ
Bode Plot
(4A Power Supply Configuration)
Bode Plot
(10A Power Supply Configuration)
5V Efficiency
(4A Power Supply Configuration)
100
80
60
40
20
0
210
180
150
120
90
100
80
60
40
20
0
210
180
150
120
90
100
Skip
PWM
80
GAIN
GAIN
60
PHASE
VIN = 5V
40
R2 = 15mΩ
L1 = 10µH
60
60
20
PHASE
-20
-40
30
-20
-40
30
1 high-side MOSFET: Si4800
1 low-side MOSFET: Si4800
0
0
0
0.01
0.1
1
4
OUTPUT CURRENT (A)
FREQUENCY (Hz)
FREQUENCY (Hz)
12V Efficiency
(4A Power Supply Configuration)
24V Efficiency
(4A Power Supply Configuration)
Efficiency
(10A Power Supply Configuration)
100
100
100
Skip
80
PWM
80
80
Skip
PWM
Skip
PWM
60
60
40
20
60
40
20
0
VIN = 12V
40
VIN = 24V
R2 = 15mΩ
L1 = 10µH
R2 = 7.5mΩ
R2 = 15mΩ
L1 = 10µH
L1 = 3.3µH
20
1 high-side MOSFET: Si4800
1 low-side MOSFET: Si4800
2 high-side MOSFETs: Si4884
2 low-side MOSFETs: Si4884
1 high-side MOSFET: Si4800
1 low-side MOSFET: Si4800
0
0
0.01
0.1
1
4
0.01
0.1
1
4
0.01
0.1
1
10
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
April 22, 2004
25
M9999-042204
MIC2182
Micrel
Package Information
PIN 1
0.157 (3.99)
0.150 (3.81)
DIMENSIONS:
INCHES (MM)
0.020 (0.51)
REF
0.020 (0.51)
0.013 (0.33)
0.050 (1.27)
BSC
45°
0.0098 (0.249)
0.0040 (0.102)
0°–8°
0.050 (1.27)
0.016 (0.40)
0.394 (10.00)
0.386 (9.80)
SEATING
PLANE
0.0648 (1.646)
0.0434 (1.102)
0.244 (6.20)
0.228 (5.79)
16-pin SOP (M)
5.40 (0.213)
5.20 (0.205)
7.90 (0.311)
DIMENSIONS:
MM (INCH)
7.65 (0.301)
0.875
(0.034) REF
6.33 (0.239)
6.07 (0.249)
2.00 (0.079)
1.73 (0.068)
10°
4°
0.22 (0.009)
0.13 (0.005)
0.38 (0.015)
0.25 (0.010)
1.25 (0.049) REF
0.21 (0.008)
0.05 (0.002)
COPLANARITY:
0.10 (0.004) MAX
0°
–8°
0.95 (0.037)
0.55 (0.022)
0.65 (0.0260)
BSC
16-Pin SSOP (SM)
M9999-042204
26
April 22, 2004
MIC2182
Micrel
April 22, 2004
27
M9999-042204
MIC2182
Micrel
MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s
use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2004 Micrel, Incorporated.
M9999-042204
28
April 22, 2004
相关型号:
MIC2182-5.0BM
Switching Controller, Current-mode, 0.1A, 330kHz Switching Freq-Max, BICMOS, PDSO16, SOP-16
MICROCHIP
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