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MIC2185
Micrel, Inc.
MIC2185
Low Voltage Synchronous Boost PWM Control IC
General Description
Micrel’s MIC2185 is a high efficiency synchronous boost
PWM control IC. With its wide input voltage range of 2.9V to
14V, the MIC2185 can be used to efficiently boost voltages
in 1- or 2-cell Li Ion battery powered applications, as well as
fixed 3.3V and 5V systems. Its powerful 5Ω output drivers
allow the MIC2185 to supply large output currents with the
selection of the proper external MOSFETs.
With it’s fixed frequency PWM architecture, and easily
synchronized drive, the MIC2185 is ideal for noise-sensi-
tive telecommunications applications. The nominal 400kHz
operating frequency of the MIC2185 can be divided by two,
allowing the device to be externally synchronized to frequen-
cies below 400kHz.
The MIC2185 also features a low current shutdown mode
and a programmable undervoltage lockout. A skipped pulse
mode of operation can be manually set to achieve higher
efficiencies at light load conditions.
The MIC2185 is available in a 16 pin SOIC package and 16
pin QSOP package with an ambient temperature operating
range from –40°C to 85°C.
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Input voltage range: 2.9V to 14V
95% efficiency
Oscillator frequency of 200kHz/400kHz
Frequency sync to 600kHz
0.5µA shutdown current
Two 5Ω output drivers
Front edge blanking
PWM current mode control
Cycle-by-cycle current limiting
Frequency foldback protection
Adjustable under-voltage lockout
Precision 1.245V reference output
16 pin SOIC narrow body package
3.3V to 5V conversion in telecom systems
Satellite phones
Cable modems
1-and 2-cell Li Ion battery operated equipment
Applications
Ordering Information
Part Number
Standard
MIC2185BM
MIC2185BQS
Pb-Free
MIC2185YM
MIC2185YQS
Frequency
200/400kHz
200/400kHz
Voltage
Adj
Adj
Junction
Temp. Range
–40ºC to +125ºC
–40ºC to +125ºC
Package
16-pin SOIC
16-pin QSOP
Typical Application
V
IN
= 3.3V
C
IN
1
7
15
10
4
8
11
2
2.4µH
Si9803DY (x2)
V
OUT
= 5V
VINA
EN/UVLO
FREQ/2
VDD
COMP
VREF
SYNC
SKIP
SS
3
OUTP
VINP
FB
MIC2185
14
16
6
C
OUT
100
5V Output Efficiency
OUTN
CSH
13
9
Si4884DY (x2)
95
90
8m
PGND
SGND
5
12
85
80
75
70
0
V
IN
= 3.3V
200kHz P WM
1
2
3
4
5
OUTPUT CURRENT (A)
Adjustable Output Synchronous Boost Converter
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
October 2005
1
MIC2185
MIC2185
Micrel, Inc.
Pin Configuration
VINA 1
SKIP 2
SS 3
COMP 4
SGND 5
FB 6
EN/UVLO 7
VREF 8
16 VINP
15 FREQ/2
14 OUTP
13 OUTN
12 PGND
11 SYNC
10 VDD
9 CSH
16-pin Narrow Body SOIC (M)
16-pin QSOP (QS)
Pin Description
Pin Number
1
2
Pin Name
VINA
SKIP
Pin Function
Input voltage to control circuitry (2.9V to 14V).
Skip (Input): Regulator operates in PWM mode (no pulse skipping) when
pin is pulled low, and skip mode when raised to VDD. There is no automatic
switching between PWM and skip mode available on this device.
Soft Start (External Component) : Reduces the inrush current and delays
and slows the output voltage rise time. A 5µA current source will charge the
capacitor up to VDD.
Compensation (Output): Internal error amplifier output. Connect to a capaci-
tor or series RC network to compensate the regulator’s control loop.
Small Signal Ground (Return) : Must be routed separately from other
grounds to the (–) terminal of C
OUT
.
3
SS
4
5
6
7
COMP
SGND
FB
EN/UVLO
Feedback (Input) : Regulates FB to 1.245V.
Enable/Undervoltaqe Lockout (Input): A low level on this pin will power down
the device, reducing the quiescent current to under 0.5µA. This pin has two
separate thresholds, below 1.5V (typical) the output switching is disabled,
and below 0.9V (typical) the device is forced into a complete micropower
shutdown. The 1.5V threshold functions as an accurate undervoltage lockout
(UVLO) with 140mV hysteresis.
Voltage Reference (Output) : The 1.245V reference is available on this pin.
A 0.1µF capacitor should be connected form this pin to SGnd.
Current Sense (Input) : The (+) input to the current limit comparator. A built
in offset of 100mV (typical) between CSH and SGnd in conjunction with the
current sense resistor sets the current limit threshold level. This is also the
(+) input to the current amplifier.
3V Internal Linear-Regulator (Output) : VDD is also the supply voltage bus
for the chip. Bypass to SGND with 1µF. Maximum source current is 0.5mA.
Frequency Synchronization (Input): Connect an external clock signal to
synchronize the oscillator. Leading edge of signal above 1.4V (typical) starts
switching cycle. Connect to SGND if not used.
MOSFET Driver Power Ground (Return) : Connects bottom of current sense
resistor and the (–) terminal of C
IN
.
N-Channel Drive (Output) : High current drive for n-channel MOSFET. Volt-
age swing is from ground to V
IN
P. On-resistance is typically 5Ω.
8
9
VREF
CSH
10
11
VDD
SYNC
12
13
14
PGND
OUTN
OUTP
P-Channel Drive (Output) : High current drive for the synchronous p-channel
MOSFET. Voltage swing is from ground to V
IN
P. On-resistance is typically
5Ω.
Frequency Divider (Input) : When this pin is low, the oscillator frequency is
400KHz. When this pin is raised to VDD, the oscillator frequency is 200KHz.
Gate Drive Voltage (Input) : This is the power input to the gate drive cir-
cuitry (2.9V to 14V). This pin is typically connected to the output voltage to
enhance gate drive.
15
16
FREQ/2
VINP
MIC2185
2
October 2005
MIC2185
Micrel, Inc.
Absolute Maximum Ratings (Note 1)
Supply Voltage (V
IN
A, V
IN
P) .......................................... 15V
Digital Supply Voltage (V
DD
)............................................ 7V
Skip Pin Voltage (V
SKIP
) ....................................–0.3V to 7V
Comp Pin Voltage (V
COMP
) ...............................–0.3V to 3V
Feedback Pin Voltage (V
FB
) ..............................–0.3V to 3V
Enable Pin Voltage (V
EN/UVLO
) .......................–0.3V to 15V
Current Sense Voltage (V
CSH
) ..........................–0.3V to 1V
Sync Pin Voltage (V
SYNC
) ................................–0.3V to 7V
Freq/2 Pin Voltage (V
FREQ/2
) .............................–0.3V to 7V
Power Dissipation (P
D
)
16 lead SOP ...................................400mW @ T
A
= 85°C
16 lead QSOP .................................245mW@ T
A
= 85°C
Ambient Storage Temp ............................. –65°C to +150°C
Operating Ratings
(Note 2)
Supply Voltage (V
IN
A, V
IN
P) ......................... +2.9V to +14V
Operating Ambient Temperature...........–40°C ≤ T
A
≤ +85°C
Junction Temperature .........................–40°C ≤ T
J
≤ +125°C
PackageThermal Resistance
θ
JA
16-lead SOP ................................................ 100°C/W
θ
JA
16-lead QSOP ............................................. 163°C/W
ESD Rating,
Note 3
Electrical Characteristics
V
IN
A= 5V, VinP= V
OUT
=12V, V
EN/UVLO
= 5V, V
SKIP
= 0V, V
FREQ/2
= 0V, V
CSH
= 0V, T
J
= 25°C, unless otherwise specified.
Bold
values
indicate –40°C < T
J
< +125°C.
Parameter
Condition
(±1%)
(±2%)
Feedback Bias Current
Output Voltage Line Regulation
Output Voltage Load Regulation
Input & V
DD
Supply
V
IN
A Input Current, PWM mode
V
IN
A Input Current, SKIP mode
Shutdown Quiescent Current
Digital Supply Voltage (VDD)
Digital Supply Load Regulation
Undervoltage Lockout
Reference Output (V
REF
)
Reference Voltage
3V ≤ V
IN
A ≤ 9V; 0mV ≤ CSH ≤ 75mV; (±3%)
3V ≤ V
IN
A ≤ 9V
Min
Typ
Max
Regulation
Feedback Voltage Reference
1.233
1.220
1.208
1.245
50
+0.08
–1.2
0.8
3.8
0.6
0.5
2.8
2.9
3.0
0.03
2.75
2.65
1.226
1.213
2
1
1.245
1.264
1.276
3.2
1.245
1.258
1.270
1.282
V
V
V
nA
%/V
%
mA
mA
mA
µA
V
V
V
V
V
V
mV
mV
Units
0mV ≤ CSH ≤ 75mV
V
SKIP
= 0V
V
SKIP
= 5V
I
L
= 0
V
IN
P Input Current, PWM mode
V
SKIP
= 0V (excluding external MOSFET gate current)
V
EN/UVLO
= 0V; (I
VINA
+ I
VINP
)
I
L
= 0 to 0.5mA
V
DD
upper threshold (turn on threshold)
V
DD
lower threshold (turn off threshold)
(±1.5%)
(±2.5%)
5V < VinA < 9V
0 < I
REF
< 100µA
Reference Voltage Line
Regulation
Reference Voltage Load
Regulation
Enable/UVLO
Enable Input Threshold
UVLO Threshold
UVLO Hysteresis
Enable Input Current
0.6
1.4
V
EN/UVLO
= 5V
0.9
1.5
140
0.2
1.2
1.6
5
V
V
mV
µA
October 2005
3
MIC2185
MIC2185
Parameter
Soft Start
Soft Start Current
Current Limit
Current Limit Threshold Voltage
Error Amplifier
Error Amplifier Gain
Current Amplifier
Current Amplifier Gain
SKIP Input
SKIP Threshold
SKIP Input Current
Oscillator Section
Oscillator Frequency (f
S
)
Maximum Duty Cycle
Minimum On Time
FREQ/2 frequency (f
S
)
Frequency Foldback Threshold
Frequency Foldback Frequency
SYNC Threshold Level
SYNC Input Current
SYNC Minimum Pulse Width
SYNC Capture Range
Gate Drivers (OUTN and OUTP)
Rise/Fall Time
Driver Non-overlap Time
Output Driver Impedance
C
L
= 3300pF
V
IN
P = 12V
V
IN
P = 5V
Note 4
200
f
O
+15 %
50
70
90
4
3
5
5
V
SKIP
= 3V
360
V
FB
= 1.0V
V
FB
= 1.5V
V
FREQ/2
=3V
170
0.6
1.4
0.1
400
85
180
200
0.3
90
0.6
1.4
0.1
3.7
20
Voltage on CSH to trip current limit
100
5
Condition
Min
Typ
Micrel, Inc.
Max
Unit
µA
mV
V/V
V/V
2.2
5
440
V
µA
kHz
%
ns
230
V
kHz
2.2
5
600
V
µA
ns
kHz
ns
ns
ns
8
7
11
11
Ω
Ω
Ω
Ω
Measured at FB pin
V
FREQ/2
=0V
Sink; V
IN
P = 12V
Sink; V
IN
P = 5V
Note 1.
Source; V
IN
P = 12V
Source; V
IN
P = 5V
Note 2.
Note 3.
Note 4.
The device is not guaranteed to function outside its operating rating.
Devices are ESD sensitive. Handling precautions recommended.
Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when
operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction tempera-
ture, T
J(max)
, the junction-to-ambient thermal resistance,
θ
JA
, and the ambient temperature, T
A
.
See application information for limitations on maximum operating frequency.
MIC2185
4
October 2005
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