MIC38C42/3/4/5
Micrel
MIC38C42/3/4/5
BiCMOS Current-Mode PWM Controllers
General Description
The MIC38C4x are fixed frequency, high performance, cur-
rent-mode PWM controllers. Micrel’s BiCMOS devices are
pin compatible with 384x bipolar devices but feature several
improvements.
Undervoltage lockout circuitry allows the ’42 and ’44 versions
to start up at 14.5V and operate down to 9V, and the ’43 and
’45 versions start at 8.4V with operation down to 7.6V. All
versions operate up to 20V.
When compared to bipolar 384x devices operating from a
15V supply, start-up current has been reduced to 50µA
typical and operating current has been reduced to 4.0 mA
typical. Decreased output rise and fall times drive larger
MOSFETs, and rail-to-rail output capability increases effi-
ciency, especially at lower supply voltages. The MIC38C4x
also features a trimmed oscillator discharge current and
bandgap reference.
MIC38C4x denotes 8-pin plastic DIP, SOIC, and MM8™
packages. MIC38C4x-1 denotes 14-pin plastic DIP and
SOIC packages. 8-pin devices feature small size, while 14-
pin devices separate the analog and power connections for
improved performance and power dissipation.
Features
• Fast 40ns output rise and 30ns output fall times
• –40°C to +85°C temperature range
meets UC284x specifications
• High-performance, low-power BiCMOS Process
• Ultralow start-up current (50µA typical)
• Low operating current (4mA typical)
• CMOS outputs with rail-to-rail swing
•
≥
500kHz current-mode operation
• Trimmed 5V bandgap reference
• Pin-for-pin compatible with UC3842/3843/3844/3845(A)
• Trimmed oscillator discharge current
• UVLO with hysteresis
• Low cross-conduction currents
Applications
•
•
•
•
•
•
•
Current-mode, off-line, switched-mode power supplies
Current-mode, dc-to-dc converters.
Step-down “buck” regulators
Step-up “boost” regulators
Flyback, isolated regulators
Forward converters
Synchronous FET converters
For fast rise and fall times and higher output drive, refer to the
MIC38HC4x.
Functional Diagram
VDD
7 (12)
*
35V
5V
Reference
UVLO
†
VREF
8 (14)
(VD)
(11)
RT/CT
4 (7)
Oscillator
T
Q
‡
OUT
6 (10)
FB
2 (3)
2R
2.5V
R
S
R
Q
(PGND)
(8)
*
COMP
1 (1)
GND*(AGND)
5
(9)
ISNS
3 (5)
( ) pins are on MIC38C4x-1 (14-lead) versions only
* MIC38C4x (8-lead) versions only
†
MIC38C42, MIC38C43 (96% max. duty cycle) versions only
‡
MIC38C44, MIC38C45 (50% max. duty cycle) versions only
MM8 is a trademark of Micrel, Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
August 2000
1
MIC38C42/3/4/5
MIC38C42/3/4/5
Micrel
Pin Configuration
MIC38C4x-1
COMP 1
NC 2
14 VREF
13 NC
12 VDD
11 VD
10 OUT
9 AGND
8 PGND
MIC38C4x
COMP 1
FB 2
ISNS 3
RT/CT 4
8
7
6
5
VREF
VDD
OUT
GND
FB 3
NC 4
ISNS 5
NC 6
RT/CT 7
8-Pin DIP (N)
8-Lead SOIC (M)
8-Lead MM8™ (MM)
14-Pin DIP (-1BN)
14-Lead SOIC (-1BM)
Pin Description
Pin Number
N, M, MM
1
Pin Number
-1BN, -1BM
1
2
2
3
4
3
5
6
4
5
8
9
6
10
11
7
12
13
8
14
7
Pin Name
COMP
NC
FB
NC
ISNS
NC
RT/CT
GND
PGND
AGND
OUT
VD
VDD
NC
VREF
Pin Function
Compensation: Connect external compensation network to modify the error
amplifier output.
Not internally connected.
Feedback (Input): Error amplifier input. Feedback is 2.5V at desired output
voltage.
Not internally connected.
Current Sense (Input): Current sense comparator input. Connect to current
sensing resistor or current transformer.
Not internally connected.
Timing Resistor/Timing Capacitor: Connect external RC network to select
switching frequency.
Ground: Combined analog and power ground.
Power Ground: N-channel driver transistor ground.
Analog Ground: Controller circuitry ground.
Power Output: Totem-pole output.
Power Supply (Input): P-channel driver transistor supply input. Return to
power ground (PGND).
Analog Supply (Input): Controller circuitry supply input. Return to analog
ground (AGND).
Not internally connected.
5V Reference (Output): Connect external RC network.
August 2000
3
MIC38C42/3/4/5
MIC38C42/3/4/5
Micrel
Absolute Maximum Ratings
Zener Current (V
DD
) ................................................... 30mA
Operation at
≥
18V may require
special precautions (Note 6).
Supply Voltage (V
DD
),
Note 6 .......................................
20V
Switch Supply Voltage (V
D
) .......................................... 20V
Current Sense Voltage (V
ISNS
) ..................... –0.3V to 5.5V
Feedback Voltage (V
FB
) ................................ –0.3V to 5.5V
Output Current, 38C42/3/4/5 (I
OUT
) ............................. 0.5A
Storage Temperature (T
A
) ....................... –65°C to +150°C
Operating Ratings
Junction Temperature (T
J
) ........................................ 150°C
Package Thermal Resistance
8-Pin Plastic DIP
(θ
JA
) ....................................... 125°C/W
8-Pin MM8™
(θ
JA
) ............................................. 250°C/W
8-Pin SOIC
(θ
JA
) ...............................................170°C/W
14-Pin Plastic DIP
(θ
JA
) ....................................... 90°C/W
14-Pin SOIC
(θ
JA
) ............................................. 145°C/W
Electrical Characteristics
V
DD
= 15V,
Note 4;
R
T
= 11.0k; C
T
= 3.3nF; –40°C
≤
T
A
≤
85°C; unless noted
Parameter
Reference Section
Output Voltage
Line Regulation
Load Regulation
Temp. Stability
Total Output Variation
Output Noise Voltage
Long Term Stability
Output Short Circuit
Oscillator Section
Initial Accuracy
Voltage Stability
Temp. Stability
Clock Ramp
Reset Current
Amplitude
Error Amp Section
Input Voltage
Input Bias Current
A
VOL
Unity Gain Bandwidth
PSRR
Output Sink Current
Output Source Current
V
OUT
High
V
OUT
Low
V
COMP
= 2.5V
V
FB
= 5.0V
2
≤
V
O
≤
4V
Note 1
12
≤
V
DD
≤
18V
V
FB
= 2.7V, V
COMP
= 1.1V
V
FB
= 2.3V, V
COMP
= 5V
V
FB
= 2.3V, R
L
= 15k to ground
V
FB
= 2.7V, R
L
= 15k to V
REF
65
0.7
60
2
–0.5
5
14
–1
6.8
0.1
1.1
2.42
2.50
–0.1
90
1.0
2.58
–2
V
µA
dB
MHz
dB
mA
mA
V
V
T
A
= 25°C,
Note 5
12
≤
V
DD
≤
18V,
Note 6
T
MIN
≤
T
A
≤
T
MAX
,
Note 1
T
A
= 25°C, V
RT/CT
= 2V
T
A
= T
MIN
to T
MAX
V
RT/CT
peak to peak
7.7
7.2
49
52
0.2
0.04
8.4
8.4
1.9
9.0
9.5
55
1.0
kHz
%
%/°C
mA
mA
Vp-p
T
A
= 25°C, I
O
= 1mA
12V
≤
V
DD
≤
18V, I
O
= 5µA,
Note 6
1
≤
I
O
≤
20mA
Note 1
Line, Load, Temp.,
Note 1
10Hz
≤
f
≤
10kHz, T
A
= 25°C,
Note 1
T
A
= 125°C, 1000 hrs.,
Note 1
–30
4.82
50
5
–80
25
–180
4.90
5.00
2
1
0.2
5.18
5.10
20
25
V
mV
mV
mV/°C
V
µV
mV
mA
Test Conditions
Min
Typ
Max
Units
MIC38C42/3/4/5
4
August 2000
MIC38C42/3/4/5
Parameter
Current Sense
Gain
MaximumThreshold
PSRR
Input Bias Current
Delay to Output
Output
R
DS(ON)
High
R
DS(ON)
Low
Rise Time
Fall Time
Undervoltage Lockout
Start Threshold
MIC38C42/4
MIC38C43/5
Minimum Operating Voltage
MIC38C42/4
MIC38C43/5
Pulse Width Modulator
Maximum Duty Cycle
MIC38C42/3
MIC38C44/5
Minimum Duty Cycle
Total Standby Current
Start-Up Current
V
DD
= 13V for MIC38C42/44
V
DD
= 7.5V for MIC38C43/45
Operating Supply Current
Zener Voltage (V
DD
)
V
FB
= V
ISNS
= 0V
I
DD
= 25mA,
Note 6
30
4.0
37
6.0
50
200
94
46
96
50
0
13.5
7.8
8
7.0
14.5
8.4
9
7.6
15.5
9.0
10
8.2
I
SOURCE
= 200mA
I
SINK
= 200mA
T
A
= 25°C, C
L
= 1nF
T
A
= 25°C, C
L
= 1nF
20
11
40
30
80
60
Notes 2, 3
V
COMP
= 5V,
Note 2
12
≤
V
DD
≤
18V,
Note 2
2.85
0.9
3.0
1
70
–0.1
120
–2
250
3.15
1.1
Test Conditions
Min
Typ
Max
Micrel
Units
V/V
V
dB
µA
ns
Ω
Ω
ns
ns
V
V
V
V
%
%
%
µA
mA
V
Note 1:
These parameters, although guaranteed, are not 100% tested in production.
Note 2:
Parameter measured at trip point of latch with V
EA
= 0.
Note 3:
Gain defined as:
A =
∆
V
PIN1
;
0
≤
V
TH
(I
SNS
)
≤
0.8V
V
TH
(I
SNS
)
Note 4:
Adjust V
DD
above the start threshold before setting at 15V.
Note 5:
Output frequency equals oscillator frequency for the MIC38C42 and MIC38C43. Output frequency for the MIC38C44, and
MIC38C45 equals one half the oscillator frequency.
Note 6:
On 8-pin version, 20V is maximum input on pin 7, as this is also the supply pin for the output stage. On 14-pin version, 40V is
maximum for pin 12 and 20V maximum for pin 11.
August 2000
5
MIC38C42/3/4/5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
