CS4124
Preliminary
CS4124
High Side PWM FET Controller
Description
The CS4124 is a monolithic integrat-
ed circuit designed primarily to
control the rotor speed of perma-
nent magnet, direct current (DC)
brush motors. It drives the gate of
an N channel power MOSFET or
IGBT with a user-adjustable, fixed
frequency, variable duty cycle,
pulse width modulated (PWM) sig-
nal. The CS4124 can also be used to
control other loads such as incan-
descent bulbs and solenoids.
Inductive current from the motor or
solenoid is recirculated through an
external diode.
The CS4124 accepts a DC level
input signal of 0 to 5V to control the
pulse width of the output signal.
This signal can be generated by a
potentiometer referenced to the on-
chip 5V linear regulator, or a fil-
tered 0% to 100% PWM signal also
referenced to the 5V regulator.
The IC is placed in a sleep state by
pulling the CTL lead below 0.5V. In
this mode everything on the chip is
shutdown except for the on-chip
regulator and the overall current
draw is less than 275µA. There are a
number of on-chip diagnostics that
look for potential failure modes and
can disable the external power
MOSFET.
Features
s
150mA Peak PWM Gate
Drive Output
s
Patented Voltage
Compensation Circuit
s
100% Duty Cycle
Capability
s
5V, ± 3% Linear Regulator
s
Low Current Sleep Mode
s
Overvoltage Protection
s
Boost Mode Power
Supply
s
Output Inhibit
Applications Diagram
Package Option
V
BAT
42.5µH
16 Lead PDIP
1000µF
1000µF
R
S
10
470µH
10K
10nF
1.5µF
C
FLT
.25µF
R
OSC
93.1K
C
OSC
470pF
OUTPUT Gnd
BOOST
INH
FLT
I
ADJ
R
OSC
C
OSC
CTL
PGnd
I
SENSE+
I
SENSE-
PMP
SNI
R
SNI
4
R
CS1
C
CS
51
.022µF
R
CS2
51
R
SENSE
4m
OUTPUT
BOOST
FLT
R
OSC
C
OSC
CTL
PGnd
V
CC
1
Gnd
INH
I
ADJ
I
SENSE+
I
SENSE-
PMP
SNI
V
REG
V
CC
100µF
.01µF
10K
1µF
P1
10K
100K
V
REG
Input
10K
R
GATE
6
10K
N1
10K
10K
10µF
1M
MOT+
MOT-
Consult Factory for 16 Lead SOIC
Wide package.
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
Rev. 4/26/99
1195
A
®
Company
CS4124
Absolute Maximum Ratings
Storage Temperature ................................................................................................................................................-65˚C to 150˚C
V
CC
.................................................................................................................................................................................-0.3V to 30V
V
CC
Peak Transient Voltage (load dump = 26V w/series 10Ω resistor) ...........................................................................40V
Input Voltage Range (at any input) ...........................................................................................................................-0.3V to 10V
Maximum Junction Temperature ..........................................................................................................................................150˚C
Lead Temperature Soldering
Wave Solder (through hole styles only) ......................................................................................10 sec. max, 260°C peak
ESD Capability (Human Body Model) ....................................................................................................................................2kV
Electrical Characteristics:
4V
≤
V
CC
≤
26V, -40˚C < T
A
< 125°C, (unless otherwise specified)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
s
V
CC
Supply
Operating Current Supply
Quiescent Current
Overvoltage Shutdown
s
Control (CTL)
Control Input Current
Sleep Mode Threshold
Sleep Mode Hysteresis
7V
≤
V
CC
≤
18V
4V
≤
V
CC
< 7V, 18V < V
CC
≤
26V
V
CC
= 12V
26.5
5
170
10
15
275
29
mA
mA
µA
V
CTL = 0V to 5V
7V
≤
V
CC
≤
26V
4V
≤
V
CC
< 7V
-2
8%
50
10
0.1
10%
100
2
12%
150
150
µA
V
REG
mV
mV
s
Current Sense
Differential Voltage Sense
7V
≤
V
CC
≤
18V
I
ADJ
= 1V and R
CS1
= 51Ω
I
ADJ
= 4V and R
CS1
= 51Ω
4V
≤
V
CC
< 7V
I
ADJ
=1V and R
CS1
= 51Ω
18V < V
CC
≤
26V
I
ADJ
= 1V and R
CS1
= 51Ω
I
ADJ
= 4V and R
CS1
= 51Ω
18
104
15
34
125
39
mV
mV
mV
15
102
-2
0.3
39
130
2
mV
mV
µA
I
ADJ
Input Current
4V
≤
V
CC
≤
26V
I
ADJ
= 0V to 5V
s
Linear Regulator
Output Voltage, V
REG
V
CC
= 4V
V
CC
= 13.2V
V
CC
= 26V
2.0
4.85
4.85
5.15
5.20
V
V
V
s
Inhibit
Inhibit Threshold
Inhibit Hysteresis
4V
≤
V
CC
≤
7V
7V
≤
V
CC
≤
26V
40%
100
150
50%
325
60%
500
500
V
REG
mV
mV
s
External Drive (OUTPUT)
Output Frequency
4V
≤
V
CC
< 7V
R
OSC
= 93.1kΩ, C
OSC
= 470pF
7V
≤
V
CC
≤
18V,
R
OSC
= 93.1kΩ, C
OSC
= 470pF
18V < V
CC
≤
26V
R
OSC
= 93.1kΩ, C
OSC
= 470pF
1196
10
17
17
20
20
25
23
25
kHz
kHz
kHz
CS4124
Electrical Characteristics:
4V
≤
V
CC
≤
26V, -40˚C < T
A
= 125°C, (unless otherwise specified)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
s
External Drive (OUTPUT): continued
Voltage to Duty Cycle
4V
≤
V
CC
< 7V
Conversion
V
CC
= 13V, CTL = 1V
V
CC
= 13V, CTL = 2V
7V
≤
V
CC
≤
18V
V
CC
= 13V, CTL = 30% V
REG
V
CC
= 13V, CTL = 55.8% V
REG
18V < V
CC
≤
26V
V
CC
= 13V, CTL = 1. 5V
V
CC
= 13V, CTL = 3. 5V
Output Rise Time
4V
≤
V
CC
≤
26V
R
GATE
= 6Ω, C
GATE
= 5nF
Output Fall Time
4V
≤
V
CC
≤
26V
R
GATE
= 6Ω, C
GATE
= 5nF
Output Sink Current
4V
≤
V
CC
< 7V
R
GATE
= 6Ω, C
GATE
= 5nF
7V
≤
V
CC
≤
26V
R
GATE
= 6Ω, C
GATE
= 5nF
Output Source Current
4V
≤
V
CC
< 7V
R
GATE
= 6Ω, C
GATE
= 5nF
7V
≤
V
CC
≤
26V
R
GATE
= 6Ω, C
GATE
= 5nF
Output High Voltage
Output Low Voltage
s
Charge Pump (DRV)
Boost Voltage
Package Lead Description
PACKAGE LEAD #
LEAD SYMBOL
65
100
28.3
56.0
11.8
34.2
.25
.30
150
300
150
300
V
BOOST
- 1.7
75
%
%
%
%
%
%
µs
µs
mA
mA
mA
mA
V
V
36.3
64.0
21.8
44.2
1
1
I
OUT
= 1mA
I
OUT
= -1mA
1.3
V
CC
+ 6.4
V
FUNCTION
16 Lead PDIP
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
OUTPUT
BOOST
FLT
R
OSC
C
OSC
CTL
PGnd
V
CC
V
REG
SNI
PMP
I
SENSE-
I
SENSE+
I
ADJ
INH
Gnd
MOSFET gate drive
Boost voltage
Fault time out capacitor
Oscillator resistor
Oscillator capacitor
Pulse width control input
Power ground for on chip clamp
Positive power supply input
5V linear regulator
Sense inductor current
Collector of boost power transistor
Current sense minus
Current sense plus
Current limit adjust
Output Inhibit
Ground
1197
CS4124
Application Information
Theory Of Operation
Oscillator
The IC sets up a constant frequency triangle wave at the
C
OSC
lead whose frequency is related to the external com-
ponents R
OSC
and C
OSC
, by the following equation:
Frequency =
0.83
R
OSC
×
C
OSC
120%
V
CC
= 8V
100%
pensated duty cycle. The transfer is set up so that when
V
CC
= 14V the duty cycle will equal V
CTL
divided by V
REG
.
For example at V
CC
= 14V, V
REG
= 5V and V
CTL
= 2.5V, the
duty cycle would be 50% at the output. This would place a
7V average voltage across the load. If V
CC
then drops to
10V, the IC would change the duty cycle to 70% and hence
keep the average load voltage at 7V.
The peak and valley of the triangle wave are proportional
to V
CC
by the following:
V
VALLEY
= 0.1
×
V
CC
V
PEAK
= 0.7
×
V
CC
This is required to make the voltage compensation function
properly. In order to keep the frequency of the oscillator
constant the current that charges C
OSC
must also vary with
supply. R
OSC
sets up the current which charges C
OSC
. The
voltage across R
OSC
is 50% of V
CC
and therefore:
I
ROSC
= 0.5
×
V
CC
R
OSC
Duty Cycle( %)
80%
V
CC
= 14V
60%
V
CC
= 16V
40%
20%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
CTL Voltage (% of V
REG
)
I
ROSC
is multiplied by (2) internally and transferred to the
C
OSC
lead. Therefore:
I
COSC
= ±
The period of the oscillator is:
T = 2C
OSC
×
V
PEAK
- V
VALLEY
I
COSC
V
CC
R
OSC
Figure 1: Voltage Compensation
5V Linear Regulator
There is a 5V, 5mA linear regulator available at the V
REG
lead for external use. This voltage acts as a reference for
many internal and external functions. It has a drop out of
approximately 1.5V at room temperature.
Current Sense and Timer
The IC differentially monitors the load current on a cycle
by cycle basis at the I
SENSE+
and I
SENSE-
leads. The differen-
tial voltage across these two leads is amplified internally
and compared to the voltage at the I
ADJ
lead. The gain, A
V
is set internally and externally by the following equation:
A
V
=
V
I(ADJ)
I
SENSE+
- I
SENSE-
=
37000
1000 + R
CS
The R
OSC
and C
OSC
components can be varied to create fre-
quencies over the range of 15Hz to 25kHz. With the sug-
gested values of 93.1kΩ and 470pF for R
OSC
and C
OSC
, the
nominal frequency will be approximately 20 kHz. I
ROSC
, at
V
CC
= 14V, will be 66.7 µA. I
ROSC
should not change over a
more than 2:1 ratio and therefore C
OSC
should be changed
to adjust the oscillator frequency.
Voltage Duty Cycle Conversion
The IC translates an input voltage at the CTL lead into a
duty cycle at the OUTPUT lead. The transfer function
incorporates Cherry Semiconductor’s patented Voltage
Compensation method to keep the average voltage and
current across the load constant regardless of fluctuations
in the supply voltage. The duty cycle is varied based upon
the input voltage and supply voltage by the following
equation:
2.8
×
V
CTL
Duty Cycle = 100%
×
V
CC
An internal DC voltage equal to:
V
DC
= (1.683
×
V
CTL
) + V
VALLEY
is compared to the oscillator voltage to produce the com-
The current limit (I
LIM
) is set by the external current sense
resistor (R
SENSE
) placed across the I
SENSE+
and I
SENSE-
ter-
minals and the voltage at the I
ADJ
lead.
1000 + R
CS
37000
V
I(ADJ)
R
SENSE
I
LIM
=
×
The R
CS
resistors and C
CS
components form a differential
low pass filter which filters out high frequency noise gen-
erated by the switching of the external MOSFET and the
associated lead noise. R
CS
also forms and error term in the
gain of the I
LIM
equation because the I
SENSE+
and I
SENSE-
leads are low impedance inputs thereby creating a good
current sensing amplifier. Both leads source 50µA while
the chip is in run mode. I
ADJ
should be biased between 1V
and 4V. When the current through the external MOSFET
1198
CS4124
Application Information: continued
exceeds I
LIM
, an internal latch is set and the output pulls
the gate of the MOSFET low for the remainder of the oscil-
lator cycle (fault mode). At the start of the next cycle, the
latch is reset and the IC reverts back to run mode until
another fault occurs. If a number of faults occur in a given
period of time, the IC “times out” and disables the MOS-
FET for a long period of time to let it cool off. This is
accomplished by charging the C
FLT
capacitor each time an
over current condition occurs. If a cycle goes by with no
overcurrent fault occurring, an even smaller amount of
charge will be removed from C
FLT
. If enough faults occur
together, eventually C
FLT
will charge up to 2.4V and the
fault latch will be set. The fault latch will not be reset until
C
FLT
discharges to 0.6V. This action will continue indefi-
nitely if the fault persists.
The off time and on time are set by the following:
Off Time = C
FLT
×
2.4V - 0.6V
4.5µA
2.4V - 0.6V
I
AVG
Sleep State
This device will enter into a low current mode (< 275µA)
when CTL lead is brought to less than 0.5V. All functions
are disabled in this mode, except for the regulator.
Inhibit
When the inhibit is greater than 2.5V the internal latch is
set and the external MOSFET will be turned off for the
remainder of the oscillator cycle. The latch is then reset at
the start of the next cycle.
Overvoltage Shutdown
The IC will disable the output during an overvoltage
event. This is a real time fault event and does not set the
internal latch and therefore is independent of the oscillator
timing (i.e. asynchronous). There is 325mV (typical) of
hysteresis on the overvoltage function. There is no under-
voltage lockout. The device will shutdown gracefully once
it runs out of headroom.
Reverse Battery
The CS4124 will not survive a reverse battery condition. A
series diode is required between the battery and the V
CC
lead for reverse battery.
Load Dump
A 10Ω resistor, (R
S
) is placed in series with V
CC
to limit the
current into the IC during 40V peak transient conditions.
On Time = C
FLT
×
where:
I
AVG
= (295.5µA
×
DC ) - [4.5µA
×
(1 - DC )]
I
AVG
= (300µA
×
DC ) - 4.5µA
DC = PWM Duty Cycle
Boost Switch Mode Power Supply
The CS4124 has an integrated boost mode power supply
which charges the gate of the external high-side MOSFET
to greater than 5V above V
CC
. Three leads are used for
voltage boost. They are Boost, PMP and SNI. The PMP
lead is the collector of a darlington tied NPN power tran-
sistor. This device charges the inductor during its on time.
The boost lead is the input to chip from the external reser-
voir capacitor. The SNI lead is the emitter of the power
NPN and is connected externally to the R
SNI
resistor.
The power supply is controlled by the oscillator. At the
start of a cycle an R-S flip flop is set the internal power
NPN transistor is turned on and energy begins to build up
in the inductor. The R
SNI
resistor sets the peak current of
the inductor by tripping a comparator when the voltage
across the resistor is 450mV. The flip flop is reset and the
inductor delivers its stored energy to the load. The ripple
voltage (V
RIPPLE
) at the Boost lead is controlled by C
BOOST
.
A snubber circuit, made up of a series resistor and capaci-
tor, is required to dampen the ringing of the inductor. A
value of 4Ω is recommended for R
SNI
.
A zener diode is needed between the boost output voltage
and the battery. This will clamp the boost lead to a speci-
fied value above the battery to prevent damage to the IC.
A 9 volt zener diode is recommended.
1199
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