IMP38C/HC/42/3/4/5
P
OWER
M
ANAGEMENT
BiCMOS Current-Mode
PWM Controllers
Key Features
N
N
N
N
N
N
N
N
N
N
N
384x Series Pinout with BiCMOS Technology
Zero Cross-Conduction Current by Design
1MHz Operation
65ns Maximum Current-Sense Delay
120µA Maximum Start-Up Current
1.5mA Maximum Operating Current
High Output Current Drive
– 1.0A, IMP38HC4x
– 0.5A, IMP38C4x
20V Maximum Supply Voltage
2.5V, 1%, Trimmed Error Amplifier Reference
Trimmed Oscillator Discharge Current
Pin-for-Pin Enhanced Replacements for Micrel
MIC38C/HC4x and GMT38C4x/HC4x
– 1MHz Operation
– No Cross-Conduction Current
– 50ns Current-Sense Delay
The IMP38C4x and IMP38HC4x are fixed frequency, high performance,
current-mode PWM controllers that are pin compatible with bipolar 384x
devices but feature improvements resulting from IMP’s BiCMOS
processing and circuit design. Notable among the improvements are zero
cross-conduction/shoot-through current, reduced start-up and operating
current, lower current-sense delay, higher frequency operation, full
supply voltage swing at the output and a 1% trimmed voltage reference.
IMP38C4x and IMP38HC4x output driver stage has zero cross-conduction
current. A proprietary output state-machine monitors each output
MOSFET and guarantees by design zero cross-conduction current. This is
an industry first for 384x PWM devices.
Under-voltage lockout (UVL) performance has been improved. When
the power supply voltage is below the startup voltage, internal circuitry
puts the output into a low impedance state. The output will sink 20mA
and remain below 1.3V, well below the turn-on threshold voltage of the
external MOSFET. Even when V
DD
drops to zero volts, the out pin will
not rise above approximately 1.3V because the output UVLO circuit is
Block Diagrams
V
DD
7 (12)
(11)
V
D
+
V
REF
8 (14)
5V
Reference
UVLO
–
+
–
RTCT
COMP
FB
4 (7)
1 (1)
T
2 (3)
Q
Oscillator
6 (10)
OUT
–
EA
2R
–
1V
R
COMP
S
R
Q
+
+
–
2.5V
Ref
+
(8)
PGND
(
) Pins Are 14-Pin Devices Only
GND 5
AGND (9)
3 (5)
ISNS
Connection Notes
IMP38C4X, IMP38HC4X (8-Pin Devices)
50% Maximum Duty Cycle:
IMP38C44, IMP38HC44, IMP38C45, IMP38HC45
96% Maximum Duty Cycle:
IMP38C42, IMP38HC42, IMP38C43, IMP38HC43
38C/HC_01.eps
© 2000 IMP, Inc.
408-432-9100/www.impweb.com
1
IMP38C/HC/42/3/4/5
powered through the out pin. Leakage current from the external
power MOSFETs will not force the PWM output to rise and turn
the external MOSFETs on.
Current-sense propagation delay time is 35ns typical, 65ns maxi-
mum, representing an up to 75 percent reduction over other 38xx
implementations.
Output stage drive is 0.5A for IMP38C4x devices. The high-drive
IMP38HC4x family is rated at 1.0A peak current drive.
Like conventional 384x controllers, the IMP38C4x and
IMP38HC4x controllers use the current-mode architecture for
superior load regulation, pulse-by-pulse current limiting and out-
put MOSFET protection. All versions operate up to 20 volts.
For maximum application flexibility, start-up voltage ranges from
14.5V to 8.4V. Start-up current has been reduced to 120µA maxi-
mum and operating current has been reduced to 1.5mA maximum.
The IMP38C4x/IMP38HC4x are available in 8-pin and 14-pin DIP
and SO packages as well as the 8-pin MicroSO package. The 14-
pin devices provide separate pins for the controller power supply
and the output driver supply. This configuration maximizes
application flexibility and performance. The 14-pin package can
also dissipate more power. Devices in the compact 8-pin packages
do not have separate output drive supply connections.
The IMP38C4x and IMP38HC4x families operate over the –40°C
to +85°C temperature range.
Pin Configuration
SO/MicroSO/DIP
COMP 1
FB 2
ISNS 3
RT/CT 4
IMP38C4x
IMP38HC4x
8 V
REF
7 V
DD
6 OUT
5 GND
38C/HC_02.eps
SO/DIP
COMP 1
NC 2
FB 3
NC 4
ISNS 5
NC 6
RT/CT 7
14 V
REF
13 NC
IMP38C4x
12 V
DD
IMP38HC4x
11 V
D
10 OUT
9 AGND
8 PGND
38C/HC_03.eps
Pin Descriptions
Pin Number
8-Pin Package
1
2
3
4
14-Pin Package
1
3
5
7
Name
COMP
FB
ISNS
RT/CT
Function
Output of the Error amplifier and input to the PWM comparator.
Inverting input of the Error Amplifier.
Current sense comparator input. It is internally limited to 1V.
Oscillator RC timing component connection. Resistor RT is connected to
V
REF
and capacitor CT is connected to ground. Different values of RT and
CT determine the maximum duty cycle.
Combined power and analog ground for 8-pin packaged devices and power
ground for 14-pin package.
High-power, totem-pole driver output. OUT pin is actively held LOW when
V
CC
is below the UVLO threshold.
Supply voltage input.
5V-reference voltage output.
Analog ground connection for 14-pin package.
Output driver supply voltage for 14-pin package.
No internal connection.
38C-HC_t01.eps
5
6
7
8
8
10
12
14
9
11
2, 4, 6, 13
GND/PGND
OUT
V
DD
V
REF
AGND
V
D
NC
2
408-432-9100/www.impweb.com
© 2000 IMP, Inc.
!S
IMP38C/HC/42/3/4/5
Ordering Information
IMP Ordering
Part Number
IMP38C42EPA
IMP38C42EPD
IMP38C42ESA
IMP38C42ESD
IMP38C42EMA
IMP38C42/D
IMP38C43EPA
IMP38C43EPD
IMP38C43ESA
IMP38C43ESD
IMP38C43EMA
IMP38C43/D
IMP38C44EPA
IMP38C44EPD
IMP38C44ESA
IMP38C44ESD
IMP38C44EMA
IMP38C44/D
IMP38C45EPA
IMP38C45EPD
IMP38C45ESA
IMP38C45ESD
IMP38C45EMA
IMP38C45/D
IMP38HC42EPA
IMP38HC42EPD
IMP38HC42ESA
IMP38HC42ESD
IMP38HC42EMA
IMP38HC42/D
IMP38HC43EPA
IMP38HC43EPD
IMP38HC43ESA
IMP38HC43ESD
IMP38HC43EMA
IMP38HC43/D
IMP38HC44EPA
IMP38HC44EPD
IMP38HC44ESA
IMP38HC44ESD
IMP38HC44EMA
IMP38HC44/D
IMP38HC45EPA
IMP38HC45EPD
IMP38HC45ESA
IMP38HC45ESD
IMP38HC45EMA
IMP38HC45/D
Package
8-Plastic DIP
14-Plastic DIP
8-SO
14-SO
8-MicroSO
DIE
8-Plastic DIP
14-Plastic DIP
8-SO
14-SO
8-MicroSO
DIE
8-Plastic DIP
14-Plastic DIP
8-SO
14-SO
8-MicroSO
DIE
8-Plastic DIP
14-Plastic DIP
8-SO
14-SO
8-MicroSO
DIE
8-Plastic DIP
14-Plastic DIP
8-SO
14-SO
8-MicroSO
DIE
8-Plastic DIP
14-Plastic DIP
8-SO
14-SO
8-MicroSO
DIE
8-Plastic DIP
14-Plastic DIP
8-SO
14-SO
8-MicroSO
DIE
8-Plastic DIP
14-Plastic DIP
8-SO
14-SO
8-MicroSO
DIE
Operating
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
– 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
– 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
– 40°C to 85°C
– 40°C to 85°C
– 40°C to 85°C
– 40°C to 85°C
Startup
Voltage
14.5V
14.5V
14.5V
14.5V
14.5V
8.4V
8.4V
8.4V
8.4V
8.4V
14.5V
14.5V
14.5V
14.5V
14.5V
8.4V
8.4V
8.4V
8.4V
8.4V
14.5V
14.5V
14.5V
14.5V
14.5V
8.4V
8.4V
8.4V
8.4V
8.4V
14.5V
14.5V
14.5V
14.5V
14.5V
8.4V
8.4V
8.4V
8.4V
8.4V
Minimum
Operating
Voltage
9.0V
9.0V
9.0V
9.0V
9.0V
7.6V
7.6V
7.6V
7.6V
7.6V
9.0V
9.0V
9.0V
9.0V
9.0V
7.6V
7.6V
7.6V
7.6V
7.6V
9.0V
9.0V
9.0V
9.0V
9.0V
7.6V
7.6V
7.6V
7.6V
7.6V
9.0V
9.0V
9.0V
9.0V
9.0V
7.6V
7.6V
7.6V
7.6V
7.6V
Maximum
Duty Cycle
96%
96%
96%
96%
96%
96%
96%
96%
96%
96%
50%
50%
50%
50%
50%
50%
50%
50%
50%
50%
96%
96%
96%
96%
96%
96%
96%
96%
96%
96%
50%
50%
50%
50%
50%
50%
50%
50%
50%
50%
Reference
Voltage
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
Peak Output
Current Drive
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
0.5A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
1.0A
38C/HC_t02.eps
For SO and MicroSO packages, append “/T” to the ordering part number for tape and reel packaging.
© 2000 IMP, Inc.
PWM Controllers
3
IMP38C/HC/42/3/4/5
Absolute Maximum Ratings
V
CC
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . 20V
V
CC
Supply Current . . . . . . . . . . . . . . . . . . . . . . 30mA
I
OUT
Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0A
Current-Sense and Feedback Inputs . . . . . . . . 0.3V to 5.5V
Operation Junction Temperature . . . . . . . . . . . +150°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . – 65°C to +150°C
Lead Soldering Temperature (10 seconds) . . . +300°C
Package Thermal Resistance
8-Pin Plastic DIP (θ
JA
) . . . . . . . . . . . . . . . . . 125°C/W
8-Pin MicroSO (θ
JA
) . . . . . . . . . . . . . . . . . . . 250°C/W
8-Pin SO (θ
JA
) . . . . . . . . . . . . . . . . . . . . . . . . 170°C/W
14-Pin Plastic DIP (θ
JA
) . . . . . . . . . . . . . . . . 90°C/W
14-Pin SO (θ
JA
) . . . . . . . . . . . . . . . . . . . . . . . 145°C/W
Note: All voltages are referenced to GND.
These are stress ratings only and functional operation is not
implied. Exposure to absolute maximum ratings for prolonged
time periods may affect device reliability.
Electrical Characteristics
Unless otherwise noted, V
CC
= 15V, RT = 10kΩ and CT = 3.3nF. Specifications are over the – 40°C to +85°C ambient temperature range.
Bold/blue
specifications indicate enhanced performance features.
Parameter
Reference
Output voltage
Line Regulation
Load Regulation
Temperature Stability
Total Reference Variation
Output Noise Voltage
Long Term Stability
Output Short Circuit
Oscillator Section
Initial Accuracy
Voltage Stability
Temperature Stability
Discharge Current
Amplitude peak-to-peak
Error Amplifier Section
Input Voltage
Input Bias Current
Open Loop Gain
Unity Gain Bandwidth
Power Supply Rejection Ratio
Output Sink Current
Output Source Current
V
OUT
High
V
OUT
Low
Symbol
V
REF
Conditions
T
A
= +25°C, I
O
= 1mA
12V
≤
V
CC
≤
18V, I
OUT
= 5µA
1mA
≤
I
O
≤
20mA
Min
4.90
Typ
5.00
2
1
0.2
Max
5.10
20
25
5.18
Units
V
mV
mV
mV/°C
V
µV
mV
mA
kHz
%
%/°C
mA
V
V
µA
dB
MHz
dB
mA
mA
TC
REF
V
N
I
SC
f
INIT
TC
OSC
V
OSC, P-P
V
IN
I
B
A
VOL
UGBW
PSRR
I
OL
I
OH
V
OH
V
OL
Note 1
Line, Load, Temperature, Note 1
10Hz
≤
f
≤
10kHz, T
A
= +25°C, Note 1
T
A
= 125°C, 1000 Hours, Note 1
– 30
T
A
= 25°C, Note 5
12V
≤
V
CC
≤
18V
Note 1
V
RT/CT
= 2V
V
RT/CT
peak-to-peak
V
COMP
= 2.5V
V
FB
= 4.5V
2V
≤
V
O
≤
4V, Note 1
Note1
V
START
≤
V
CC
≤
V
CCMAX
V
FB
= 2.7V, Vcomp = 1.1V
V
FB
= 2.3V, Vcomp = 5.0V
V
FB
= 2.3V, R
L
= 15kΩ to ground
V
FB
= 2.7V, R
L
= 15kΩ to V
REF
7.2
1.1
2.45
–1
65
0.7
60
2
– 0.5
4.5
49
4.82
50
TBD
– 40
52
0.2
0.04
8.4
1.7
2.50
90
1.0
6
– 1.0
4.6
0.30
5.0
0.50
12.0
2.3
2.55
1
– 180
55
1.0
V
V
4
408-432-9100/www.impweb.com
© 2000 IMP, Inc.
!S
IMP38C/HC/42/3/4/5
Electrical Characteristics
Unless otherwise noted, V
CC
= 15V, R
T
= 10kΩ and C
T
= 3.3nF. Specifications are over the – 40°C to +85°C ambient temperature range.
Bold/blue
specifications indicate enhanced performance features.
Parameter
Current Sense
Gain
Over Current Protection Threshold
Power Supply Rejection Ratio
Input Bias Current
Delay to Output
Output
IMP38C4x
ON Resistance, High
ON Resistance, Low
IMP38HC4x
ON Resistance, High
ON Resistance, Low
Peak Drive Current
IMP38C4x Rise Time
IMP38C4x Fall Time
IMP38HC4x Rise Time
IMP38HC4x Fall Time
Shoot-through Current
Undervoltage Lockout
Start Threshold
Minimum Operating Voltage
Pulse Width Modulator
Maximum Duty Cycle
Maximum Duty Cycle
Minimum Duty Cycle
Supply Current
Start-Up Current
Operating Current
Symbol
A
VOL
PSRR
I
B
T
PD
Conditions
Notes 1, 2 and 3
Vcomp = max, Note 2
V
START
≤
V
CC
≤
18V
V
FB
= 0V, ISNS 0V to 2V, C
L
= 1nF
Min
2.90
0.9
Typ
3.00
0.98
70
– 0.1
50
Max
3.10
1.1
– 2.0
65
Units
V/V
V
dB
µA
ns
R
DS (ON)
I
SOURCE
= 0.2A
I
SINK
= 0.2A
I
SOURCE
= 0.2A
I
SINK
= 0.2A
HC devices
H devices
T
A
= 25°C, C
L
= 1nF
T
A
= 25°C, C
L
= 1nF
T
A
= 25°C, C
L
= 1nF
T
A
= 25°C, C
L
= 1nF
20
11
10
5.5
1.0
0.5
40
30
20
15
0
13.5
7.8
8
7.0
94
48
14.5
8.4
9
7.6
96
50
0
70
50
50
40
Ω
R
DS (ON)
Ω
A
ns
ns
ns
ns
mA
V
V
T
R
T
F
T
R
T
F
IMP38C42/4, IMP38HC42/4
IMP38C43/5, IMP38HC43/5
IMP38C42/4, IMP38HC42/4
IMP38C43/5, IMP38HC43/5
IMP38C42/3, IMP38HC42/3,
IMP38C44/5, IMP38HC44/5
15.5
9.0
10
8.2
%
%
%
µA
mA
I
CC
V
CC
= 13V for IMP38C42/44, IMP38HC42/44
V
CC
= 7.5V for IMP38C43/45, IMP38HC43/45
V
FB
= V
IS
= 0
95
0.5
120
1.5
Note 1. Guaranteed by design. Not 100% tested in production.
Note 2. Measured at trip point of V
FB
= 0V.
Note 3. Gain is defined as:
A
=
∆
V
COMP
, 0
≤
V
CS
≤
0.8V
∆
V
CS
Note 4. Adjust V
CC
above the start threshold before setting at 15V.
Note 5. Output frequency equals the oscillator frequency for
IMP38C42/3 and IMP38HC42/3 devices. Output frequency
equals one-half the oscillator frequency for IMP38C44/5 and
IMP38HC44/5 devices.
Table 1. Startup and Operating Voltage Selection Guide
UVLO Thresholds
Duty Cycle
0% to 96%
0% to 50%
Start-up at 8.4V
Operating Minimum = 7.6V
IMP38C43/HC43
IMP38C45/HC45
Start-up at 14.5V
Operating Minimum = 9.0V
IMP38C42/HC42
IMP38C44/HC44
38C/HC_t03.eps
© 2000 IMP, Inc.
PWM Controllers
5
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