Cherry CS51024ED16 Enhanced current mode pwm controller Datasheet

CS51021/22/23/24
CS51021/CS51023
CS51022/CS51024
Enhanced Current Mode
PWM Controller
Features
Description
The CS51021/22/23/24 Fixed
Frequency PWM Current Mode
Controller family provides all necessary features required for AC-DC or
DC-DC primary side control.
Several features are included eliminating the additional components
needed to implement them externally. In addition to low start-up current (75µA) and high frequency
operation capability, the CS51021/
22/23/24 family includes overvoltage and undervoltage monitoring,
externally programmable dual
Device
threshold overcurrent protection,
current sense leading edge blanking, current slope compensation,
accurate duty cycle control and an
externally available 5V reference.
The CS51021 and CS51023 feature
bidirectional synchronization capability, while the CS51022 and
CS51024 offer a sleep mode with
100µA maximum IC current consumption. The CS51021/22/23/24
family is available in a 16 lead narrow body SO package.
Sleep/Synch
VCC Start/Stop
CS51021
Synch
8.25V/7.7V
CS51022
Sleep
8.25V/7.7V
CS51023
Synch
13V/7.7V
CS51024
Sleep
13V/7.7V
Typical Application Diagram
100
VIN (36V to 72V)
PGND
1µF
BAS21
51k
SYNC/SLEEP
18V
22µF
11V
100:1
0.1µF
FZT688
200K,1%
24.3K
1%
10
10K
4700pF
22K
51K
VC
VREF
COMP
VFB
RTCT
SYNC/
SLEEP
CSS
330pF
LGnd
U1
PGnd
VOUT
(5V/5A)
100µF 100µF
680pF
OV
BA521
SGND
100pF
ISET
0.01µF
2:5
2.49K,1%
UV
SLOPE
GATE
ISENSE
MBRB2060CT
10
VCC
CS51021/51022
0.01µF
4:1
10K
6.98k, 6.98k, 100
1%
1%
100p
Package Options
16 Lead SO Narrow
IRF6345
10
■ 75µA Max. Startup Current
■ Fixed Frequency Current
Mode Control
■ 1MHz Switching Frequency
■ Undervoltage Protection
Monitor
■ Overvoltage Protection
Monitor with
Programmable Hysteresis
■ Programmable Dual
Threshold Overcurrent
Protection with Delayed
Restart
■ Programmable Soft Start
■ Accurate Maximum Duty
Cycle Limit
■ Programmable Slope
Compensation
■ Leading Edge Current
Sense Blanking
■ 1A Sink/Source Gate Drive
■ Bidirectional Synchronization
(CS51021/23)
■ 50ns PWM Propagation
Delay
■ 100µA Max Sleep Current
(CS51022/24)
62
GATE
ISENSE
10
470pF
TL431
VCC
VREF
2K, 1%
1000pF
1K
PGnd
SLEEP
or SYNC
SLOPE
0.1µF 5.1K
180
VC
1
2K,1%
10K
UV
LGnd
OV
SS
RTCT
ISET
MOC81025
1K
COMP
VFB
Consult factory for other package options.
36-72V to 5V, 5A DC-DC Convertor
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: [email protected]
Web Site: www.cherry-semi.com
Rev. 2/22/99
1
A
®
Company
CS51021/22/23/24
Absolute Maximum Ratings
Power Supply Voltage, VCC ............................................................................................................................................-0.3V, 20V
Driver Supply Voltage, VC ..............................................................................................................................................-0.3V, 20V
SYNC, SLEEP, RTCT, SOFT START, VFB, SLOPE, ISENSE, UV, OV, ISET (Logic Pins).......................................-0.25V to VREF
Peak GATE Output Current.........................................................................................................................................................1A
Steady State Output Current..................................................................................................................................................± 0.2A
Operating Junction Temperature, TJ ..................................................................................................................................... 150°C
Storage Temperature Range, TS ...................................................................................................................................-65 to 150°C
ESD (Human Body Model).........................................................................................................................................................2kV
Lead Temperature Soldering: Reflow (SMD styles only).............................................60 sec. max above 183°C, 230°C peak
Electrical Characteristics: Unless otherwise stated, specifications apply for -40°C < TA < 85°C, -40°C < TJ < 150°C,
3V < VC < 20V, 8.2V < VCC < 20V, RT = 12kΩ, CT = 390pF.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
8.8
13.4
8.2
1.00
6
75
V
V
V
V
V
µA
■ Under Voltage Lockout
START Threshold (CS51021/22)
START Threshold (CS51023/24)
STOP Threshold
Hysteresis (CS51021/22)
Hysteresis (CS51023/24)
ICC @ Startup (CS51021/22)
VCC < UVSTART Threshold
8.25
13
7.7
0.75
5
40
ICC @ Startup (CS51023/24)
VCC < UVSTART Threshold
45
75
µA
ICC Operating (CS51021/23)
7
9
mA
ICC Operating (CS51022/24)
6
8
mA
Includes 1nF Load
7
12
mA
Initial Accuracy
TA = 25C, IREF = 2mA, VCC = 14V (Note1) 4.95
5
5.05
V
Total Accuracy
1mA<IREF<10mA
5
5.15
V
Line Regulation
8.2V < VCC < 18V, IREF = 2mA
6
20
mV
Load Regulation
1mA < IREF < 10mA
6
15
mV
NOISE Voltage
OP Life Shift
FAULT Voltage
(Note 1)
T=1000 Hours (Note 1)
Force VREF
.92 × VREF
OK Voltage
Force VREF
.94 × VREF .96 × VREF .98 × VREF
OK Hysteresis
Force VREF
50
Current Limit
Force VREF
-20
IC Operating
7.95
12.4
7.4
0.50
4
■ Voltage Reference
4.9
50
4
20
.95 × VREF .97 × VREF
105
160
uV
mV
V
V
mV
mA
■ Error Amplifier
Initial Accuracy
TA=25°C, IREF = 2mA, VCC = 14V,
VFB = COMP (Note 1)
2.465
2.515
2.565
V
Reference Voltage
VFB = COMP
2.440
2.515
2.590
V
VFB Leakage Current
VFB = 0V
-0.2
-2
µA
Open Loop Gain
Unity Gain Bandwidth
COMP Sink Current
1.4V < COMP < 4V (Note 1)
(Note 1)
COMP = 1.5V, VFB = 2.7V
60
1.5
2
90
2.5
6
dB
MHz
mA
COMP Source Current
COMP = 1.5V, VFB = 2.3V
-0.2
-0.5
mA
2
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
■ Error Amplifier continued
COMP High Voltage
VFB = 2.3V
4.35
4.8
5
V
COMP Low Voltage
VFB = 2.7V
0.4
0.8
1.2
V
PS Ripple Rejection
SS Clamp, VCOMP
FREQ = 120Hz (Note 1)
VSS=2.5V, VFB = 0V, ISET = 2V
60
2.4
85
2.5
2.6
dB
V
ILIM(SET) Clamp
(Note 1)
0.95
1
1.15
V
Accuracy
RT = 12k, CT = 390pF
230
255
280
kHz
Voltage Stability
Delta Frequency 8.2V < VCC < 20V
2
3
%
Temperature Stability
TMIN < TA < TMAX (Note1)
8
Min Charge & Discharge Time
Duty Cycle Accuracy
(Note1)
RT = 12k, CT = 390pF
Peak Voltage
Valley Voltage
Valley Clamp Voltage
(Note 1)
(Note 1)
10k Resistor to ground on RTCT
Discharge Current
Discharge Current
TA=25°C (Note 1)
■ Oscillator
0.333
70
77
%
83
µs
%
1.2
3
1.5
1.4
1.6
V
V
V
0.8
0.925
1
1
1.2
1.075
mA
mA
1.5
260
4.3
2.7
360
4.8
V
ns
V
■ Synchronization (CS51021/23)
Input Threshold
Output Pulsewidth
Output High Voltage
ISYNC = 100µA
1.0
160
3.5
Input Resistance
Drive Delay
Output Drive Current
(Note 1)
SYNC to GATE RESET
1k Load
35
80
1.25
70
120
2
140
150
3.5
kΩ
ns
mA
SLEEP Input Threshold
SLEEP Input Current
Active High
VSLEEP = 4V
1.0
11
1.5
25
2.7
46
V
µA
ICC @ SLEEP
VCC ≤ 15V
50
100
µA
HIGH Voltage
Measure VC-GATE, VC = 10V, 150mA Load
1.5
2.2
V
LOW Voltage
HIGH Voltage Clamp
Measure GATE-PGnd, 150mA SINK
VC = 20V, 1nF
1.2
13.5
1.5
16
V
V
LOW Voltage Clamp
Peak Current
Measured at 10mA Output Current
VC = 20V, 1nF (Note 1)
0.6
1
0.8
V
A
UVL Leakage
VC = 20V, measured at 0V
-1
-50
µA
RISE Time
Load = 1nF, 1V < GATE < 9V,
VC = 20V, TA = 25˚C
60
100
ns
FALL Time
Load = 1nF, 9V > GATE > 1V, VC = 20V
15
40
ns
■ SLEEP (CS51022/24)
■ GATE Driver
3
11
CS51021/22/23/24
Electrical Characteristics: -40°C < TA < 85°C, -40°C < TJ < 150°C, 3V < VC < 20V, 8.2V < VCC < 20V,
RT = 12kΩ, CT = 390pF, unless otherwise stated
CS51021/22/23/24
Electrical Characteristics: Unless otherwise stated, specifications apply for -40°C < TA < 85°C, -40°C < TJ < 150°C,
3V < VC < 20V, 8.2V < VCC < 20V, RT = 12kΩ, CT = 390pF.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
■ SLOPE Compensation
Charge Current
SLOPE = 2V
COMP Gain
Fraction of slope voltage added
to ISENSE (Note 1)
Discharge Voltage
SYNC = 0V
-63
-53
-43
µA
0.095
0.100
0.105
V/V
0.1
0.2
V
0.10
0.11
V
55
160
ns
1.8
2
2.2
V
1.21
1.33
1.45
V/V
■ Current Sense
OFFSET Voltage
(Note 1)
0.09
Blanking Time
Blanking Disable Voltage
Adjust VFB
Second Current Threshold Gain
ISENSE Input Resistance
5
Minimum On Time
GATE High to Low
Gain
(Note 1)
kΩ
30
70
110
ns
0.78
0.80
0.82
V/V
2.4
2.5
2.6
V
OV Hysteresis Current
-10
-12.5
-15
µA
UV Monitor Threshold
1.38
1.45
1.52
V
UV Monitor Hysteresis
25
75
100
mV
-40
µA
■ OV & UV Voltage Monitors
OV Monitor Threshold
■ SOFT START (SS)
Charge Current
SS = 2V
-70
-55
Discharge Current
SS = 2V
250
1000
µA
Charge Voltage, VSS
4.4
4.7
5
V
Discharge Voltage, VSS
0.25
0.27
0.30
V
Note 1: Guaranteed by Design, not 100% tested in production.
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
16L PDIP & SO Narrow
1
GATE
External power switch driver with 1.0A peak capability.
2
ISENSE
Current sense amplifier input.
3
SYNC
(CS51021/23)
Bi-directional synchronization. Locks to the highest frequency.
3
SLEEP
(CS51022/24)
Active high chip disable. In sleep mode, VREF and GATE are
turned off.
4
SLOPE
Additional slope to the current sense signal. Internal current
source charges the external capacitor.
5
UV
Undervoltage protection monitor.
6
OV
Overvoltage protection monitor.
4
PACKAGE PIN #
PIN SYMBOL
FUNCTION
16L PDIP & SO Narrow
7
RTCT
Timing resistor RT and capacitor CT determine oscillator frequency and maximum duty cycle, DMAX.
8
ISET
Voltage at this pin sets pulse-by-pulse overcurrent threshold, and
second threshold (1.33 times higher) with Soft Start retrigger (hiccup mode).
9
VFB
Feedback voltage input. Connected to the error amplifier inverting input.
10
COMP
Error amplifier output. Frequency compensation network is usually connected between COMP and VFB pins.
11
SS
Charging external capacitor restricts error amplifier output voltage during the start or fault conditions (hiccup).
12
LGnd
Logic ground.
13
VREF
5.0V reference voltage output.
14
VCC
Logic supply voltage.
15
PGnd
Output power stage ground connection.
16
VC
Output power stage supply voltage.
Block Diagram
VCC
-
LGnd
VREF
Vcc_OK
START
STOP
+
VREF = 5V
VREF_OK
VC
+
SLEEP
4.75V
200ns
4.3V
SYNC
OSC
RTCT
Q
S
G2
D4
F1
SS
Clamp
G1
D2
ZD1
13.5V
R
ISET
Clamp
COMP
PGnd
D3
+
2.5V
20k
E/A
-
D1
VFB
VREF
53µA
55µA
+
×
0.1
×
ISENSE
Q2
–
∑
0.1V
+
SS
SS
Monitor
G4
2V
DISABLE
SLOPE
VREF
PWM
Comp
10k
VFB
Monitor
–
+
4.7V
55ns
Blank
–
VISense
0.8
2nd
Threshold
1.33
ISET
GATE
×
VREF
G3
FAULT
Discharge
Latch
12.5µA
OV
UV
UV
Monitor
OV
Monitor
+
+
1.45V
2.5V
–
–
Figure 1: CS51021/22/23/24 Block Diagram
5
CS51021/22/23/24
Package Pin Description: continued
CS51021/22/23/24
Circuit Description
Blanking is disabled when VFB is less than 2V so that the
minimum on-time of the controller does not have an additional 55ns of delay time during fault conditions. For the
remaining portion of the switching period, the current
sense signal, combined with a fraction of the slope compensation voltage, is applied to the positive input of the
PWM comparator where it is compared with the divided
by three error amplifier output voltage. The pulse-bypulse overcurrent protection threshold is set by the voltage at the ISET pin. This voltage is passed through the ISET
Clamp and appears at the non-inverting input of the PWM
comparator, limiting its dynamic range according to the
following formula:
Overcurrent Threshold= 0.8 × VI(SENSE) +0.1V + 0.1 VSLOPE
200ns
4.3V
SYNC
RTCT
TCH
TDIS
0V
VSLOPE
SLOPE
0V
IS
0V
IS + 0.1 SLOPE
IS
55ns Blanking
0V
where
VCOMP
VI(SENSE) is voltage at the ISENSE pin
PWM COMP
and
VSLOPE is voltage at the SLOPE pin.
During extreme overcurrent or short circuit conditions,
the slope of the current sense signal will become much
steeper than during normal operation. Due to loop propagation delay, the sensed signal will overshoot the pulseby-pulse threshold eventually reaching the second overcurrent protection threshold which is 1.33 times higher
than the first threshold and is described by the following
equation:
GATE
0V
VDS
VIN
0V
2nd Threshold = 1.33 × VI(SET)
Figure 2: Typical Waveforms
Exceeding the second threshold will reset the Soft Start
capacitor CSS and reinitiate the Soft Start sequence, repeating for as long as the fault condition persists.
Theory of Operation
Powering the IC
The IC has two supply and two ground pins. VC and
PGnd pins provide high speed power drive for the external power switch. VCC and LGnd pins power the control
portion of the IC. The internal logic monitors the supply
voltage, VCC. During abnormal operating conditions, the
output is held low. The CS51021/22/23/24 requires only
75µA of startup current.
Soft Start
During power up, when the output filter capacitor is discharged and the output voltage is low, the voltage across
the Soft Start capacitor (VSS) controls the duty cycle. An
internal current source of 55µA charges CSS. The maximum error amplifier output voltage is clamped by the SS
Clamp. When the Soft Start capacitor voltage exceeds the
error amplifier output voltage, the feedback loop takes
over the duty cycle control. The Soft Start time can be estimated with the following formula:
Voltage Feedback
The output voltage is monitored via the VFB pin and is
compared with the internal 2.5V reference. The error
amplifier output minus one diode drop is divided by 3
and connected to the negative input of the PWM comparator. The positive input of the PWM comparator is connected to the modified current sense signal. The oscillator
turns the external power switch on at the beginning of
each cycle. When current sense ramp voltage exceeds the
reference side of PWM comparator, the output stage latches off. It is turned on again at the beginning of the next
oscillator cycle.
tSS = 9 × 104 × CSS
The Soft Start voltage, VSS, charges and discharges
between 0.25V and 4.7V.
Slope Compensation
DC-DC converters with current mode control require a
current sense signal with slope compensation to avoid
instability at duty cycles greater than 50%. Slope capacitor
CS is charged by an internal 53µA current source and is
discharged during the oscillator discharge time. The slope
compensation voltage is divided by 10 and is added to the
current sense voltage, VI(SENSE). The signal applied to the
Current Sense and Protection
The current is monitored at the ISENSE pin. The
CS51021/22/23/24 has leading edge blanking circuitry
that ignores the first 55ns of each switching period.
6
input of the PWM comparator is a combination of these
dVSLOPE
two voltages. The slope compensation,
, is calcudt
lated using the following formula:
VIN
R2
VUV
dVSLOPE
53µA
= 0.1 × C
dt
S
R3
VOV
Figure 4: UV/OV Monitor Divider
To calculate the OV/UV resistor divider:
1. Solve for R3, based on OV hysteresis requirements.
It should be noted that internal capacitance of the IC will
cause an error when determining slope compensation
capacitance CS. This error is typically small for large values of CS, but increases as CS becomes small and comparable to the internal capacitance. The effect is apparent as a
reduction in charging current due to the need to charge
the internal capacitance in parallel with CS. Figure 3 shows
a typical curve indicating this decrease in available charging current.
VOV(HYST) × 2.5V
’
R3 = V
MAX × 12.5µA
where VOV(HYST) is the desired amount of overvoltage hysteresis, and VMAX is the input voltage at which the supply
will shut down.
2. Find the total impedance of the divider.
VMAX × R3
RTOT = R1 + R2 + R3 =
2.5
60
Charging Current (µA)
R1
55
50
3. Determine the value of R2 from the UV threshold conditions.
1.45 × RTOT
R2 =
− R3,
VMIN
45
40
35
where VMIN is the UV voltage at which the supply will
shut down.
30
25
20
10
100
4. Calculate R1.
1000
R1 = RTOT − R2 − R3
Compensation Cap (pF)
5. The undervoltage hysteresis is given by:
Figure 3: The slope compensation pin charge current reduces when a
small capacitor is used.
VUV(HYST) =
Undervoltage (UV) and Overvoltage (OV) Monitor
Two independent comparators monitor OV and UV conditions. A string of three resistors is connected in series
between the monitored voltage (usually the input voltage)
and ground (see Figure 4). When voltage at the OV pin
exceeds 2.5V, an overvoltage condition is detected and
GATE shuts down. An internal 12.5µA current source
turns on and feeds current into the external resistor, R3,
creating a hysteresis determined by the value of this resistor (the higher the value, the greater the hysteresis). The
hysteresis voltage of the OV monitor is determined by the
following formula:
VMIN × 0.075
1.45
Synchronization
A bi-directional synchronization is provided to synchronize several controllers. When SYNC pins are connected
together, the converters will lock to the highest switching
frequency. The fastest controller becomes the master, producing a 4.3V, 200ns pulse train. Only one, the highest frequency SYNC signal, will appear on the SYNC line.
Sleep
The sleep input is an active high input. The CS51022/51024
is placed in sleep mode when SLEEP is driven high. In
sleep mode, the controller and MOSFET are turned off.
Connect to Gnd for normal operation. The sleep mode
operates at VCC ≤ 15V.
VOV(HYST) = 12.5µA × R3
where R3 is a resistor connected from the OV pin to ground.
When the monitored voltage is low and the UV pin is less
than 1.45V, GATE shuts down. The UV pin has fixed 75mV
hysteresis.
Both OV and UV conditions are latched until the Soft Start
capacitor is discharged. This way, every time a fault condition is detected the controller goes through the power
up sequence.
Oscillator and Duty Cycle Limit
The switching frequency is set by RT and CT connected to
the RTCT pin. CT charges and discharges between 3V and
1.5V.
The maximum duty cycle is set by the ratio of the on time,
tON, and the whole period, T = tON + tOFF. Because the
7
CS51021/22/23/24
Circuit Description: continued
timing capacitor’s discharge current is trimmed, the maximum duty cycle is well defined. It is determined by the
ratio between the timing resistor RT and the timing capacitor CT. Refer to figures 5 and 6 to select appropriate values
for RT and CT.
1
fSW = T
; TSW = tCH + tDIS
SW
100
8
7
6
5
90
4
Duty Cycle (%)
80
2500
3
2
70
1. CT = 47pF
2. CT = 100pF
3. CT = 150pF
4. CT = 220pF
5. CT = 390pF
6. CT = 470pF
7. CT = 560pF
8. CT = 680pF
1
60
1
2000
Frequency (kHz)
CS51021/22/23/24
Circuit Description: continued
50
1. CT = 47pF
2. CT = 100pF
3. CT = 150pF
4. CT = 220pF
5. CT = 390pF
6. CT = 470pF
7. CT = 560pF
8. CT = 680pF
1500
2
40
5
4
500
5
6
5
7
10
15
20
25
30
35
40
20
25
30
35
40
45
50
Figure 6: Duty Cycle vs. RT for Discrete Capacitor Values.
3
0
15
RT (kΩ)
1000
8
10
45
50
RT (kΩ)
Figure 5: Frequency vs. RT for Discrete Capacitor Values.
8
55
PACKAGE THERMAL DATA
PACKAGE DIMENSIONS IN mm (INCHES)
D
Lead Count
16L SO Narrow
Metric
Max
Min
10.00
9.80
Thermal Data
English
Max Min
.394 .386
16L SO Narrow
RΘJC
typ
28
˚C/W
RΘJA
typ
115
˚C/W
Surface Mount Narrow Body (D); 150 mil wide
4.00 (.157)
3.80 (.150)
6.20 (.244)
5.80 (.228)
0.51 (.020)
0.33 (.013)
1.27 (.050) BSC
1.75 (.069) MAX
1.57 (.062)
1.37 (.054)
1.27 (.050)
0.40 (.016)
0.25 (.010)
0.19 (.008)
D
0.25 (0.10)
0.10 (.004)
REF: JEDEC MS-012
Ordering Information
Part Number
CS51021ED16
CS51021EDR16
CS51022ED16
CS51022EDR16
CS51023ED16
CS51023EDR16
CS51024ED16
CS51024EDR16
Rev. 2/22/99
Description
16L SO Narrow
16L SO Narrow (tape & reel)
16L SO Narrow
16L SO Narrow (tape & reel)
16L SO Narrow
16L SO Narrow (tape & reel)
16L SO Narrow
16L SO Narrow (tape & reel)
Cherry Semiconductor Corporation reserves the
right to make changes to the specifications without
notice. Please contact Cherry Semiconductor
Corporation for the latest available information.
9
© 1999 Cherry Semiconductor Corporation
CS51021/22/23/24
Package Specification
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