MIC38HC42/3/4/5
Micrel
August 2000
1
MIC38HC42/3/4/5
MIC38HC42/3/4/5
BiCMOS 1A Current-Mode PWM Controllers
General Description
The MIC38HC4x family are fixed frequency current-mode
PWM controllers with 1A drive current capability. Micrel's
BiCMOS devices are pin-compatible with 384x bipolar de-
vices. Their high output drive, with fast rise and fall times,
combined with low startup current make it an ideal PWM
controller where high efficiency is required.
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 UC384x devices operating from a
15V supply, start-up current has been reduced to 50
A
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 MIC38HC4x
also features a trimmed oscillator discharge current and
bandgap reference.
MIC38HC4x-1 is available in 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.
Functional Diagram
Features
Fast 20ns output rise and 15ns output fall times
40
C to +85C temperature range
exceeds UC284x specifications
High-performance, low-power BiCMOS Process
Ultralow start-up current (50
A typical)
Low operating current (4mA typical)
High output drive (1A peak current, HC version)
CMOS outputs with rail-to-rail swing
Current-mode operation up to 500kHz
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
T
Q
S
R
Q
R
2R
Oscillator
UVLO
5V
Reference
VDD
7 (12)
VREF
8 (14)
RT/CT
4 (7)
FB
2 (3)
2.5V
COMP
1 (1)
GND*(AGND)
5 (9)
ISNS
3 (5)
(VD)
(11)
OUT
6 (10)
(PGND)
(8)
( ) pins are on MIC38HC4x-1 (14-lead) versions only
* MIC38HC4x (8-lead) versions only
MIC38HC42, MIC38HC43 (96% max. duty cycle) versions only
MIC38HC44, MIC38HC45 (50% max. duty cycle) versions only
35V
*
*
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
MIC38HC42/3/4/5
Micrel
MIC38HC42/3/4/5
2
August 2000
Ordering Information
Part Number
Temperature Range
Package
MIC38HC42BN
40
C to +85C
8-pin Plastic DIP
MIC38HC43BN
40
C to +85C
8-pin Plastic DIP
MIC38HC44BN
40
C to +85C
8-pin Plastic DIP
MIC38HC45BN
40
C to +85C
8-pin Plastic DIP
MIC38HC42-1BN
40
C to +85C
14-pin Plastic DIP
MIC38HC43-1BN
40
C to +85C
14-pin Plastic DIP
MIC38HC44-1BN
40
C to +85C
14-pin Plastic DIP
MIC38HC45-1BN
40
C to +85C
14-pin Plastic DIP
MIC38HC42BM
40
C to +85C
8-pin SOIC
MIC38HC43BM
40
C to +85C
8-pin SOIC
MIC38HC44BM
40
C to +85C
8-pin SOIC
MIC38HC45BM
40
C to +85C
8-pin SOIC
MIC38HC42-1BM
40
C to +85C
14-pin SOIC
MIC38HC43-1BM
40
C to +85C
14-pin SOIC
MIC38HC44-1BM
40
C to +85C
14-pin SOIC
MIC38HC45-1BM
40
C to +85C
14-pin SOIC
UVLO Thresholds
Startup 8.4V
Startup 14.5V
Duty Cycle
Minimum Operating 7.6V
Minimum Operating 9V
0% to 96%
MIC38HC43
MIC38HC42
0% to 50%
MIC38HC45
MIC38HC44
Selection Guide
MIC38HC42/3/4/5
Micrel
August 2000
3
MIC38HC42/3/4/5
Pin Description
Pin Number
Pin Number
Pin Name
Pin Function
N, M, MM
-1BN, -1BM
1
1
COMP
Compensation: Connect external compensation network to modify the error
amplifier output.
2
NC
Not internally connected.
2
3
FB
Feedback (Input): Error amplifier input. Feedback is 2.5V at desired output
voltage.
4
NC
Not internally connected.
3
5
ISNS
Current Sense (Input): Current sense comparator input. Connect to current
sensing resistor or current transformer.
6
NC
Not internally connected.
4
7
RT/CT
Timing Resistor/Timing Capacitor: Connect external RC network to select
switching frequency.
5
GND
Ground: Combined analog and power ground.
8
PGND
Power Ground: N-channel driver transistor ground.
9
AGND
Analog Ground: Controller circuitry ground.
6
10
OUT
Power Output: Totem-pole output.
11
VD
Power Supply (Input): P-channel driver transistor supply input. Return to
power ground (PGND).
7
12
VDD
Analog Supply (Input): Controller circuitry supply input. Return to analog
ground (AGND).
13
NC
Not internally connected.
8
14
VREF
5V Reference (Output): Connect external RC network.
1
2
3
4
8
7
6
5
COMP
FB
ISNS
RT/CT
VREF
VDD
OUT
GND
MIC38HC4x
2
NC
NC
13
3
FB
VDD
12
4
NC
VD
11
5
ISNS
OUT
10
6
NC
AGND
9
7
RT/CT
PGND
8
1
COMP
VREF
14
MIC38HC4x-1
8-Pin DIP (N)
8-Lead SOIC (M)
14-Pin DIP (-1BN)
14-Lead SOIC (-1BM)
Pin Configuration
MIC38HC42/3/4/5
Micrel
MIC38HC42/3/4/5
4
August 2000
Electrical Characteristics
V
DD
= 15V, Note 4; R
T
= 9.09k
; C
T
= 3.3nF; 40
C T
A
85C; unless noted
Parameter
Test Conditions
Min
Typ
Max
Units
Reference Section
Output Voltage
T
A
= 25
C, I
O
= 1mA
4.90
5.00
5.10
V
Line Regulation
12V
V
DD
18V, I
O
= 5
A, Note 6
2
20
mV
Load Regulation
1
I
O
20mA
1
25
mV
Temp. Stability
Note 1
0.2
mV/
C
Total Output Variation
Line, Load, Temp., Note 1
4.82
5.18
V
Output Noise Voltage
10Hz
f 10kHz, T
A
= 25
C, Note 1
50
V
Long Term Stability
T
A
= 125
C, 1000 hrs., Note 1
5
25
mV
Output Short Circuit
30
80
180
mA
Oscillator Section
Initial Accuracy
T
A
= 25
C, Note 5
49
52
55
kHz
Voltage Stability
12
V
DD
18V, Note 6
0.2
1.0
%
Temp. Stability
T
MIN
T
A
T
MAX
, Note 1
0.04
%/
C
Clock Ramp
T
A
= 25
C, V
RT/CT
= 2V
7.7
8.4
9.0
mA
Reset Current
T
A
= T
MIN
to T
MAX
7.2
8.4
9.5
mA
Amplitude
V
RT/CT
peak to peak
1.9
Vp-p
Error Amp Section
Input Voltage
V
COMP
= 2.5V
2.42
2.50
2.58
V
Input Bias Current
V
FB
= 5.0V
0.1
2
A
A
VOL
2
V
O
4V
65
90
dB
Unity Gain Bandwidth
Note 1
0.7
1.0
MHz
PSRR
12
V
DD
18V
60
dB
Output Sink Current
V
FB
= 2.7V, V
COMP
= 1.1V
2
14
mA
Output Source Current
V
FB
= 2.3V, V
COMP
= 5V
0.5
1
mA
V
OUT
High
V
FB
= 2.3V, R
L
= 15k to ground
5
6.8
V
V
OUT
Low
V
FB
= 2.7V, R
L
= 15k to V
REF
0.1
1.1
V
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, 38HC42/3/4/5 (I
OUT
) .............................. 1A
Operating Junction Temperature (T
J
) ....................... 150
C
Package Thermal Resistance
8-Pin Plastic DIP
(
JA
) ....................................... 125
C/W
8-Pin MM8TM
(
JA
) ............................................. 250
C/W
8-Pin SOIC
(
JA
) ............................................... 170
C/W
14-Pin Plastic DIP
(
JA
) ....................................... 90
C/W
14-Pin SOIC
(
JA
) ............................................. 145
C/W
Storage Temperature (T
A
) ....................... 65
C to +150C
MIC38HC42/3/4/5
Micrel
August 2000
5
MIC38HC42/3/4/5
Parameter
Test Conditions
Min
Typ
Max
Units
Current Sense
Gain
Notes 2, 3
2.85
3.0
3.15
V/V
MaximumThreshold
V
COMP
= 5V, Note 2
0.9
1
1.1
V
PSRR
12
V
DD
18V, Note 2
70
dB
Input Bias Current
0.1
2
A
Delay to Output
120
250
ns
Output
R
DS(ON)
`HC' High
I
SOURCE
= 200mA
10
R
DS(ON)
`HC' Low
I
SINK
= 200mA
5.5
Rise Time
T
A
= 25
C, C
L
= 1nF
20
50
ns
Fall Time
T
A
= 25
C, C
L
= 1nF
15
40
ns
Undervoltage Lockout
Start Threshold
MIC38HC42/4
13.5
14.5
15.5
V
MIC38HC43/5
7.8
8.4
9.0
V
Minimum Operating Voltage
MIC38HC42/4
8
9
10
V
MIC38HC43/5
7.0
7.6
8.2
V
Pulse Width Modulator
Maximum Duty Cycle
MIC38HC42/3
94
96
%
MIC38HC44/5
46
50
%
Minimum Duty Cycle
0
%
Total Standby Current
Start-Up Current
V
DD
= 13V, 38HC42/44
50
200
A
V
DD
= 7.5V, 38HC43/45
Operating Supply Current
V
FB
= V
ISNS
= 0V
4.0
6.0
mA
Zener Voltage (V
DD
)
I
DD
= 25mA, Note 6
30
37
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
V
(I
)
0
V
(I
)
0.8V
PIN1
TH
SNS
TH
SNS
;
Note 4: Adjust V
DD
above the start threshold before setting at 15V.
Note 5: Output frequency equals oscillator frequency for the MIC38HC42 and MIC38HC43. Output frequency for the MIC38HC44, and
MIC38HC45 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.
PDF 
ZIP