MIC38HC42/3/4/5
Micrel, Inc.
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 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 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.
Features
• Fast 20ns output rise and 15ns output fall times
• –40°C to +85°C temperature range
exceeds UC284x specifications
• High-performance, low-power BiCMOS Process
• Ultralow start-up current (50µA 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
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 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
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
April 2005
1
M9999-042205
MIC38HC42/3/4/5
Micrel, Inc.
Pin Configuration
MIC38HC4x-1
COMP 1
NC 2
FB 3
14 VREF
13 NC
12 VDD
11 VD
10 OUT
9 AGND
8 PGND
MIC38HC4x
COMP 1
FB 2
ISNS 3
RT/CT 4
8
7
6
5
VREF
VDD
OUT
GND
NC 4
ISNS 5
NC 6
RT/CT 7
8-Pin DIP (N)
8-Lead SOIC (M)
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.
April 2005
3
M9999-042205
MIC38HC42/3/4/5
Micrel, Inc.
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
(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
Storage Temperature (T
A
) ....................... –65°C to +150°C
Electrical Characteristics
V
DD
= 15V,
Note 4;
R
T
= 9.09kΩ; 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
M9999-042205
4
April 2005
MIC38HC42/3/4/5
Parameter
Current Sense
Gain
MaximumThreshold
PSRR
Input Bias Current
Delay to Output
Output
R
DS(ON)
‘HC’ High
R
DS(ON)
‘HC’ Low
Rise Time
Fall Time
Undervoltage Lockout
Start Threshold
MIC38HC42/4
MIC38HC43/5
Minimum Operating Voltage
MIC38HC42/4
MIC38HC43/5
Pulse Width Modulator
Maximum Duty Cycle
MIC38HC42/3
MIC38HC44/5
Minimum Duty Cycle
Total Standby Current
Start-Up Current
V
DD
= 13V, 38HC42/44
V
DD
= 7.5V, 38HC43/45
V
FB
= V
ISNS
= 0V
I
DD
= 25mA,
Note 6
30
50
94
46
96
50
13.5
7.8
8
7.0
14.5
8.4
9
7.6
I
SOURCE
= 200mA
I
SINK
= 200mA
T
A
= 25°C, C
L
= 1nF
T
A
= 25°C, C
L
= 1nF
10
5.5
20
15
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
Test Conditions
Min
Typ
Micrel, Inc.
Max
Units
3.15
1.1
V/V
V
dB
–2
250
µA
ns
Ω
Ω
50
40
ns
ns
15.5
9.0
10
8.2
V
V
V
V
%
%
0
%
200
µA
mA
V
Operating Supply Current
Zener Voltage (V
DD
)
4.0
37
6.0
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 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.
April 2005
5
M9999-042205
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