View R2A20121SP_4374834.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

R2A20121SP
Synchronous Phase Shift Full-Bridge Control IC
REJ03D0914-0100 Rev.1.00 Sep 29, 2008
Features
* * * * * High frequency operation; oscillator frequency = 2 MHz Max Full-bridge phase-shift switching circuit with adjustable delay times Integrated secondary synchronous rectification control with adjustable delay times Pulse by pulse current limit Package: TSSOP-20
Illustrative Circuit
VIN Vout
+
DC 5 V DC 5 V DC 5 V DC 5 V DC 5 V Vbias (DC 12 V)
-
VCC OUT OUT CS RAMP -A -B
OUT -C
OUT OUT OUT -D -E -F COMP
R2A20121
VREF GND RT SYNC SS FB (+) FB (-) DELAY DELAY DELAY -3 -1 -2 HAT3043C HAT3042C HAT3004R Note: The above circuit is reference example. Please confirm the operation when designing the system.
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 1 of 27
R2A20121SP
Pin Arrangement
SYNC RAMP CS COMP FB (+) FB (-) SS DELAY-1 DELAY-2 DELAY-3 1 2 3 4 5 6 7 8 9 10 (Top view) 20 19 18 17 16 15 14 13 12 11 RT GND OUT-A OUT-B OUT-C OUT-D OUT-E OUT-F VCC VREF
Pin Functions
Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Pin Name SYNC RAMP CS COMP FB (+) FB (-) SS DELAY-1 DELAY-2 DELAY-3 VREF VCC OUT-F OUT-E OUT-D OUT-C OUT-B OUT-A GND RT Function Synchronization I/O for the oscillator Current sense signal input for the full-bridge control loop Current sense signal input for OCP Error amplifier output Error amplifier plus input Error amplifier minus input Timing capacitor for soft-start Delay time adjustor for the full-bridge control signal (OUT-A and B) Delay time adjustor for the full-bridge control signal (OUT-C and D) Delay time adjustor for the secondary control signal (OUT-E and F) 5 V/20 mA Output IC power supply input Secondary control signal Secondary control signal Full-bridge control signal Full-bridge control signal Full-bridge control signal Full-bridge control signal Ground level for the IC Timing resistor for the oscillator
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 2 of 27
R2A20121SP
Block Diagram
VCC
H UVLO L VCC > 8.4 VHigh
UVL
5V GENERATOR VREF H GOOD L VREF > 4.6 VHigh
VREF
VREF RT Current Ref. Generator OSCILLATOR RES SYNC SYNC. I/O ERROR AMP VREF FB (-) FB (+) COMPARATOR
+ -
START-UP COUNTER 32 CLOCK
VREF GOOD
CIRCUIT BIAS VREF
DELAY
OUT-A DELAY-1 OUT-B VREF
Q DELAY
VREF
500
R SQ
COMP 1.135 V RAMP CLAMP CIRCUIT VREF
SS
CS
Note: Note that all switches in the block diagram are turned on when control signal is high.
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 3 of 27
- +
DELAY
OUT-C
DELAY-2 VREF DELAY OUT-D
1.55 V 1.46 V VREF GOOD
-
+
R Q S 4V 10
Zero Delay
VREF GOOD DELAY
VREF OUT-E DELAY-3 VREF OUT-F
+
PULSE BY PULSE
Zero Delay DELAY
1.4 V
-
GND
R2A20121SP
Absolute Maximum Ratings
(Ta = 25C)
Item Power supply voltage Peak output current DC output current VREF output current COMP sink current DELAY set current RT set current VREF terminal voltage Terminal group 1 voltage Operating junction temperature Storage temperature Notes: 1. 2. 3. 4. 5. Symbol Vcc Ipk-out Idc-out Iref-out Isink-comp Iset-delay Iset-rt Vter-ref Vter-1 Tj-opr Tstg Ratings 20 50 5 -20 2 0.3 0.3 -0.3 to 6 -0.3 to (Vref + 0.3) -40 to +125 -55 to +150 Unit V mA mA mA mA mA mA V V C C Notes 1 2, 3 3 3 3 3 3 1, 4 1, 5 6
Rated voltages are with reference to the GND pin. Shows the transient current when driving a capacitive load. For rated currents, inflow to the IC is indicated by (+), and outflow by (-). VREF pin voltage must not exceed VCC pin voltage. Terminal group 1 is defined the pins; CS, RAMP, COMP, FB (+), FB (-), SS, RT, SYNC, DELAY-1 to 3, OUT-A to F 6. ja; 228C/W Board condition; Glass epoxy 55 mm x 45 mm x 1.6 mm, 10% wiring density.
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 4 of 27
R2A20121SP
Electrical Characteristics
(Ta = 25C, Vcc = 12 V, RT = 33 k, Rdelay = 51 k, unless otherwise specified.)
Item SUPPLY Start threshold Shutdown threshold UVLO hysteresis Start-up current Operating current VREF Output voltage Line regulation Load regulation Temperature stability OSCILLATOR Oscillator frequency Switching frequency Line stability Temperature stability RT voltage SYNC Input threshold Output high Output low Minimum input pulse Output pulse width VH VL dVUVL Is Icc Vref Vref-line Vref-load dVref/dTa fosc fsw fsw-line dfsw/dTa VRT VTH-SYNC VOH-SYNC VOL-SYNC TI-MIN TO-SYNC Symbol Min 7.7 7.4 0.3 -- -- 4.9 -- -- -- -- 412 -1.5 -- 2.5 2.5 3.5 -- 50 -- Typ 8.4 8.0 0.4 90 7 5.0 0 6 80 * 960 * 480 0 0.1 * 2.7 2.85 4.0 0.05 -- 500
1 1 1
Max 9.1 8.6 0.5 150 10 5.1 10 20 -- -- 547 1.5 -- 2.9 3.2 -- 0.15 -- --
Unit V V V A mA V mV mV ppm/C kHz kHz % %/C V V V V ns ns
Test Conditions
Vcc = 7.5 V No load on VREF pin Vcc = 10 V to 16 V Iref = -1 mA to -20 mA Ta = -40 to 105C Measured on OUT-A, -B Vcc = 10 V to 16 V Ta = -40 to 105C
RSYNC = 33 k to GND RSYNC = 33k to VREF
Note:
1. Reference values for design. Not 100% tested in production.
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 5 of 27
R2A20121SP
Electrical Characteristics (cont.)
(Ta = 25C, Vcc = 12 V, RT = 33 k, Rdelay = 51 k, unless otherwise specified.)
ERROR AMPLIFIER Item Input offset voltage FB (+) input current FB (-) input current Open-loop DC gain Unity gain bandwidth Output source current Output sink current Output high voltage Output low voltage Output clamp voltage * PHASE MODULATOR
4
Symbol Vos IFB (+) IFB (-) Av BW ISOURCE ISINK VOH-EO VOL-EO VCLAMP-EO VRAMP IRAMP ISINK-RAMP Dmin Dmax Tpd Tdis TD1, 2, 3 TD2_1, _2, _3 VD1, 2, 3
Min -2 -2.0 -2.0 -- -- -650 2.0 3.7 -- -0.16 1.035 -5 8 -- -- -- 40 22 70 1.9
Typ 3 0 0 1 80 * 1 2* -500 6.5 3.9 0.1 -0.07 1.135 -0.8 26 15 0** 15 97.0 * * 30 80 33.5 100 2.0
Max 8 2.0 2.0 -- -- -390 -- -- 0.4 0.0 1.235 5 -- -- -- 60 120 45 130 2.1
Unit mV A A dB MHz A mA V V V V A mA % % ns ns ns ns V
Test Conditions
FB (-) and COMP are shorted. VFB (+) = 1.25 V FB (+) = FB (-) = 1.25 V FB (+) = FB (-) = 1.25 V
FB (+) = 1.25 V, FB (-) = 0.75 V, COMP = 2 V FB (+) = 1.25 V, FB (-) = 1.75 V, COMP = 2 V FB (+) = 1.25 V, FB (-) = 0.75 V, COMP; Open FB (+) = 1.25 V, FB (-) = 1.75 V, COMP; Open FB (+) = 1.25 V, FB (-) = 0.75 V, COMP; Open, SS = 1 V RAMP = 0.3 V RAMP = 1 V, COMP = 0 V RAMP = 1 V, COMP = 0 V RAMP = 0 V, COMP = 2.1 V COMP = 1.6 V Delay set R = 51 k Delay set R = 180 k Delay set R = 51 k
DELAY
RAMP offset voltage RAMP bias current 1 RAMP sink current * Minimum phase shift Maximum phase shift 2 Delay to OUT-C, -D * 1 RAMP discharge time * 3 DELAY-1, -2, -3 * 13 DELAY2-1, -2, -3 * * Terminal voltage
Notes: 1. Reference values for design. Not 100% tested in production. 2. Tpd is defined as; 1V RAMP 50% 0V 5V 50% OUT-C/D 0V
Tpd
3. TD1, 2, 3 are defined as;
TD1 TD1
OUT-A
For primary control
OUT-B OUT-C
50%
TD2
TD2
OUT-D
For secondary control
OUT-E
TD3
OUT-F
TD3
4. VCLAMP-EO = VCOMP - SS voltage (1 V) 5. Maximum/Minimum phase shift is defined as;
D=
T2 x 2 x 100 (%) T1
OUT-B
T2 T2
OUT-A OUT-D
T1
OUT-C
T1
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 6 of 27
R2A20121SP
Electrical Characteristics (cont.)
(Ta = 25C, Vcc = 12 V, RT = 33 k, Rdelay = 51 k, unless otherwise specified.)
Item SOFT START OVER CURRENT PROTECTION OUTPUT Source current SS high voltage Pulse-by-pulse current limit threshold Delay to OUT pins * High voltage Low voltage Rise time Fall time Timing offset *
3 2
Symbol ISS VOH-SS VCS-PP Tpd-cs VOH-OUT VOL-OUT tr tf TD4
Min -14 3.9 1.26 -- 4.3 -- -- -- --
Typ -10 4.0 1.4 40 4.8 0.1 5 5 3
Max -6 4.1 1.54 80 -- 0.4 15 15 20
Unit A V V ns V V ns ns ns
Test Conditions SS = 1 V
CS = 0 V to 1.57 V IOUT = -5 mA IOUT = 5 mA COUT = 33 pF COUT = 33 pF
Notes: 1. Reference values for design. Not 100% tested in production. 2. Tpd-cs is defined as; 1.57 V 50% CS 0
OUT-C/D
Tpd-cs
50%
3. TD4 is defined as;
OUT-D OUT-E
50% 50% TD4
OUT-C OUT-F
50% 50% TD4
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 7 of 27
R2A20121SP
Timing Diagram
Note: All voltage, current, time shown in the diagram is typical value. Full Bridge and Secondary Control
COMP RAMP + 1.135 V
(Internal signal)
1.135 V
RAMP CS
TD1 TD1
OUT-A OUT-B OUT-C
TD2 TD2
OUT-D
TD3
OUT-E OUT-F
TD3
VIN
OUT-A
DRIVE
MA
MC
DRIVE
OUT-C
OUT-B
DRIVE
MB
MD
DRIVE
OUT-D
RAMP
DRIVE
ME MF
DRIVE
OUT-E External Power Stage
OUT-F
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 8 of 27
R2A20121SP Start-up and Shutdown
8.4 V VCC
8V
5V VREF 0V RES (Internal signal) VREF GOOD (Internal signal) SS 0V DISCHARGE (Internal signal) High Low High Low 4.0 V
32 counts
From Error Amp COMP COMPARATOR
+ -
FOR PHASE MODULATION RAMP Current information CLAMP VREF 4.0 V Iss 10 A SS IN Css DISCHARGE 1.135 V
SS
Soft-start Block
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 9 of 27
R2A20121SP
Functional Description
Note: All voltage, current, time shown in the diagram is typical value unless otherwise noted. UVLO UVLO (Under Voltage Lockout Operation) is a function that halts operation of the IC in the event of a low IC power supply voltage. When IC operation is halted, the 5 V internal voltage generation circuit (VREF) halts, and therefore operation of circuitry using VREF as the operating power supply halts. Circuit blocks other than UVLO use VREF as their operating power supply. Therefore, the power supply current of the IC becomes equal to the current dissipated by the UVLO circuit. The following graphs show the relationship between the VCC input current and VCC input voltage, and between VREF and the VCC input voltage.
ICC
ICC
Is
0 7.5 V 8.0 V 8.4 V 12 V 20 V
VCC
VREF
5V
VCC
0 8.0 V 8.4 V 20 V
Figure 1 Start-up Counter When the VREFGOOD signal (internal signal) goes to the logic low level, the R2A20121 starts operating as a controller. The VREFGOOD signal is created from VREFGOOD circuit output via a 32-clock startup counter.
VCC
H L
VREF
UVLO 5V Generator VREF GOOD H L
From Oscillator
Start-up Counter 32 clock
VREF GOOD
Circuit Bias
Figure 2 Therefore, the start of IC operation is a 32-count later than UVLO release. When the oscillator frequency is set to 1 MHz, this represents a delay of 32 s. This delay enables operation to be halted until VREF (5 V) stabilizes when UVLO is released. Note that the start-up counter operates when VREF rises is performed, but does not operate when VREF falls is performed (there is no logic delay due to the start-up counter).
8.4 V 8.0 V
VCC
4.6 V
VREF RES
(Internal signal)
4.4 V 32 counts
VREF GOOD
(Internal signal)
Start of operation
Operation halted
Figure 3
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 10 of 27
R2A20121SP Oscillator The oscillation frequency of the oscillator is set by means of a resistance connected between the RT pin and GND. The following graph shows the relationship between the external resistance and the oscillation frequency. The typical value of the oscillation frequency is given by the following equation.
fosc =
1 25 [pF] x RT [] + 150 [ns]
fosc vs. RT
[Hz]
10000
R2A20121 SYNC
fosc (kHz)
1000
(2.7 V)
100
RT GND
RT
10 10 100 RT (k) 1000
Figure 4 Place the resistor for connection to the RT pin as close to the pin as is possible. Please design the pattern so that the level of cross-talk from other signals is minimized.
Synchronized Operation Parallel synchronized operation is possible by connecting the SYNC pins of R2A20121s. In this case, up to four slave ICs can be connected to one master IC. A value of at least twice the master RT value should be set for the slave IC RT values.
R2A20121 MASTER (2.7 V) RT SYNC GND R2A20121 SLAVE SYNC GND RT (2.7 V)
RT
2 x RT
R2A20121 SLAVE SYNC GND Max 4 slaves RT (2.7 V)
2 x RT
Figure 5 Parallel Synchronized Operation
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 11 of 27
R2A20121SP External synchronized operation is possible by supplying a synchronization signal to the SYNC pins of R2A20121s. In this case, a frequency not exceeding 1/2 that of the master clock should be set for the R2A20121s. A maximum master clock frequency of 2 MHz should be used. See the figure below for the input waveform conditions.
TTL or CMOS MASTER
MASTER CLOCK
R2A20121 SLAVE SYNC GND RT (2.7 V)
RT
R2A20121 SLAVE SYNC GND RT (2.7 V)
RT
Figure 6 External Synchronized Operation
TCYCLE TI-MIN TIH-SYNC Item TCYCLE TI-MIN TIL-MIN VIH-SYNC TIL-SYNC TIL-MIN VIL-SYNC Input Range 500 ns Min 50 ns Min 100 ns Min 3.2 V to VREF 0 V to 2.5 V
Figure 7 SYNC Pin Input Conditions
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 12 of 27
R2A20121SP Noise Margin When a synchronization signal is given to an SYNC terminal of the R2A20121, the oscillation frequency of the IC may occur abnormality by the slew rate of the synchronization signal and the noise level of the VREF terminal. The following graph shows the relationship between the slew rate of the synchronization signal and the VREF noise level. In the case of synchronized operation, a VREF capacitor should be chosen with reference to the following graph.
R2A20121 Noise Margin
11 10 9
SYNC Slew Rate [V/s]
8 7 6 5 4 3 2 1 0 100
Area of normal operation
150
200 250 300 VREF Noise Level [mVp-p]
350
400
Note: The upper graph is a measurement result by our evaluation jig. Please confirm enough evaluation because the influence of the noise is different with each board.
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 13 of 27
R2A20121SP RAMP Capacitance Setting Method The following graph shows the relationship between the RAMP capacitance and discharge time. A RAMP capacitance should be chosen with reference to the following graph.
R2A20121 Discharge Time vs. RAMP Capacitance
140
120
100
Discharge Time [ns]
80
60
40
20
0
0
300
400
500
600
700
800
900
1300
1400
RAMP Capacitance [pF]
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 14 of 27
1500
100
200
1000
1100
1200
R2A20121SP Synchronous Phase Shift Full-Bridge Control The R2A20121 is provided with full-bridge control outputs OUT-A through OUT-D, and secondary-side synchronous rectification control outputs OUT-E and OUT-F. ZVS (Zero Voltage Switching) can be performed by adjusting timing delays TD1 and TD2 between the OUT-A through OUT-D outputs by means of an external resistance. OUT-E and OUT-F have an output timing suitable for secondary-side full-wave rectification, and so can be used in either current doubler or center tap applications. The following figure shows full-bridge ZVS + current doubler operation using an ideal model.
RES pulse (Internal signal) SA Full-Bridge control switch (on when high) TD1 SB SC TD2 SD Synchronous rectification control switch (on when high) Transformer primary both-side voltage SE TD3 SF VIN 0 -VIN
Transformer VIN/N secondary 0 -VIN/N both-side voltage Subinterval : Time : t0 1 t1 2 t2 3 t3 4 t4 5 t5
Figure 8 * Subinterval: 1 In interval 1, SA and SD are turned on, and VIN is generated on the transformer primary side. On the transformer secondary side, a value proportional to the winding ratio is generated, and the primary-side power is transmitted to the load side. At this time, secondary-side switch SE is off and SF is on.
VIN SA V11 Lr Cr1 SB SD Cr2 SF SC V12 SE VOUT L1
L2
Subinterval: 1
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 15 of 27
R2A20121SP * Subinterval: 2 As SD is turned off at point t1, the primary-side current flows into resonant capacitance Cr2. At this time Cr2 is charged, and therefore the potential of V12 rises. Considering that the exciting current and the L1 and L2 ripple currents are considerable smaller than Io, the following is an approximate equation for the slope of V12.
dV12 dt = 0.5 Io N * 1 Cr2 [ V/s ] ........................ (1)
Here, N is the ratio of the primary coil to the secondary coil (N = N1/N2), and Io is the output current. As SE and SF are on, the transformer secondary side is in the shorted state, and the value of the current flowing up to that time is retained.
VIN SA V11 Lr Cr1 SB SD Cr2 SF SC V12 SE VOUT L1
L2
Subinterval: 2 * Subinterval: 3 SC is turned on at point t2. ZVS operation can be attained by setting the SD off (t1) SC on (t2) delay to the optimal value. This delay time can be expressed by equation (2).
TD2 = N 0.5 Io * Cr2 * VIN [s] ........................ (2)
After SC is turned on, the transformer primary side is in the shorted state, and therefore the current value immediately after SC was turned on is retained.
VIN SA V11 Lr Cr1 SB SD Cr2 SF SC V12 SE VOUT L1
L2
Subinterval: 3 * Subinterval: 4 As SA is turned off at point t3, the primary-side current discharges resonant capacitance Cr1, and the potential of V11 falls. A negative potential is applied to resonant inductor Lr, and a flux reset starts. At this time, since the series resonance circuit is composed of Cr1 and Lr, the V11 waveform changes to a sine wave. The resonance frequency is given by equation (3).
fr = 1 2 (Cr1 * Lr) [Hz] ........................ (3)
VIN SA V11 Lr Cr1 SB SD Cr2 SF SC V12 SE
L1
VOUT
L2
Subinterval: 4
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 16 of 27
R2A20121SP * Subinterval: 5 When synchronous switch SF is turned off at point t4, the current flowing in SF up to that time continues to flow through the SF body diode. SF turn-off must be performed before completion of the resonant inductor Lr flux reset. If SF is not off on completion of the Lr flux reset, power transmission will be performed with the transformer secondary-side shorted, and therefore an excessive current will flow in the transformer primary and secondary sides, and parts may be damaged. Also, if the SF body diode is on for a long period, loss will be high. Therefore, optimal timing should be set by means of the R2A20121's delay adjustment pin, DELAY-3. Lr reset time tr is given by equation (4) when the resonance voltage peak value is within the input voltage.
Treset (Lr) | vpp VIN = 1 1 * fr 4
= 0.5
(Lr * Cr1)
[s] ............ (4)
Here, vpp is the resonance voltage peak value.
vpp = Io 2 * 1 * N
(Lr / Cr1)
[V] ........................ (5)
VIN SA V11 Lr Cr1 SB SD Cr2 SF SC V12 SE
L1
VOUT
L2
Subinterval: 5 * Time: t5 SB is turned on at point t5. The SB switching loss can be minimized by turning on SB when the SB both-side voltages are at a minimum (when the resonance voltage is at a peak). The SB turn-on timing can be set with TD1 of the R2A20121. The time when the resonance voltage is at a peak is given by equation (4). From t5 onward, operation is on the same principle as in Subinterval 1 through Subinterval 5.
VIN SA V11 Lr Cr1 SB SD Cr2 SF SC V12 SE VOUT L1
L2
Time: t5
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 17 of 27
R2A20121SP Delay Setting Inter-output delays (TD1, TD2, TD3) are set by means of a resistance connected between the DELAY-1 (-2, -3) pin and GND. The following graph shows the relationship between the external resistance and delay. The typical value of the delay set time is given by the following equation.
TD = 0.5 [pF] x RD [] + 8 [ns]
[s]
When the RD value is small, the set time will be larger than the above calculated value due to the effect of internal delay, etc., and therefore a constant setting should be made with reference to the following graph.
TD vs. RD
1.00E+03
R2A20121
TD (ns)
1.00E+02
(2.0 V)
1.00E+01
RD
1.00E+00 1 10 100 1000
DELAY-1 (DELAY-2) (DELAY-3) GND
RD (k)
Figure 9 Place the resistor for connection to the DELAY-1,2,3 pin as close to the pin as is possible. Please design the pattern so that the level of cross-talk from other signals is minimized.
DELAY-3 (TD3) There is a condition that secondary-side control output OUT-E and OUT-F delay TD3 is 0 s (typical) in order to prevent shorting of the transformer secondary side. The relationship between TD3 and the IC operating state is shown in the following table.
Mode Light load Pulse by pulse OCL Definition COMP < 1.55 V CS 1.4 V Operation of OUT-E, OUT-F TD3 = 0 TD3 = 0 Notes 1, 3 2, 3
Notes: 1. Light-load detection is performed by means of the error amplifier output voltage. Light-load detection characteristics are as shown in the following diagram. VREF Error Light Load 500 Amp. TD3 Detector - FB (-) - TD3 + + set value FB (+)
Comparator
COMP
- +
0 1.46 V 1.55 V
COMP voltage
RAMP
1.135 V
Light Load Detector Characteristics
2. TD3 of the next OUT-E or OUT-F after the pulse-by-pulse current limiter (PBP OCL) operates is 0 s (typical). When OUT-C and OUT-D are subsequently inverted by the Phase Shift Comparator, not the PBP OCL, TD3 is restored to the value set by means of the DELAY-3 pin. 3. If once the SS terminal is not exceed 3.9 V after an IC started, the IC continues maintaining a state in TD3 = 0. When an external part is attached to the SS terminal, please be careful.
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 18 of 27
R2A20121SP
Application
Note: All voltage, current, time shown in the diagram are typical value. Sample application circuits are given here. Confirmatory experiments should be carried out when applying these examples to products. Slope Compensation In order to improve the unstable operation characteristic of current mode, voltage slopes in a current sense signal can be superimposed. The following is a possible slope compensation method.
5 V (VREF) OUT-A OUT-D OUT-B OUT-C Comparator
- +
R2A20121
1.135 V Current sense signal Compensated signal RAMP S Q R RES
Figure 10 Driving a Pulse Transformer OUT-A through OUT-F of this IC are CMOS outputs that use Vref as their power supply. When directly driving a pulse transformer, the Vref voltage fluctuates according to the exciting current. As Vref fluctuation may make internal circuit operation unstable, direct drive of a pulse transformer should be avoided. * Case 1 (NG) The figure below shows a case where a pulse transformer is driven directly. Vref voltage fluctuation occurs due to the exciting current.
R2A20121 Vref value fluctuates due to this exiting current
Vref Cref Internal Circuitry
OUT-E
Case 1 (NG) * Case 2 The figure below shows an example in which a current amplifier is added by means of transistors. A reverse current due to the exciting current is prevented by a blocking diode, and therefore capacitance CB is charged. In this way, fluctuation of the Cref potential is suppressed and stable operation can be achieved. As well as a buffer implemented by means of a transistor, standard logic IC or buffer IC connection is also possible. The buffer circuit power supply method should be implemented in the same way.
Blocking diode R2A20121
Vref Cref Internal Circuitry CB
OUT-E
Case 2
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 19 of 27
R2A20121SP * Case 3 The figure below shows an example of a drive power supply method using emitter following. For the same reason as described above, fluctuation of the Cref potential is suppressed and stable operation can be achieved.
VCC
R2A20121
CB
VREF Cref Internal Circuitry OUT-E
Case 3 Supplying Power from an External Power Supply It is also possible to use an external source as the power supply for the R2A20121 as shown in figure 11. The VREFGOOD circuit controls whether the IC is operating or stopped. The threshold voltage of the VREFGOOD circuit is 4.6 V (typ.) on the rising edge and 4.4 V on the falling edge. Since the IC's characteristics vary with the value of the external voltage, this voltage must be provided by a high-precision 5-V source.
Vcc Vext 5 V 2% VREF R2A20121
Figure 11
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 20 of 27
R2A20121SP
Characteristic Curves
UVL Voltage vs. Ambient Temperature Characteristics
9.0 8.8 8.6
[V]
VH
8.4 8.2
VL
VH/VL
8.0 7.8 7.6 7.4
-40 -25 0 25 Ta 50 [C] 75 100 125
Standby Current vs. Ambient Temperature Characteristics
140
Vcc = 7.5 V
120
100
80
Is [A]
60
40
20
0 -40
-25
0
25 Ta
50 [C]
75
100
125
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 21 of 27
R2A20121SP
Operating Current vs. Ambient Temperature Characteristics
12
10
8
Icc [mA]
6
4
2
0 -40
-25
0
25 Ta
50 [C]
75
100
125
VREF Output Voltage vs. Ambient Temperature Characteristics
5.20 5.15 5.10 5.05
VREF [V]
5.00 4.95 4.90 4.85 4.80 -40
-25
0
25 Ta
50 [C]
75
100
125
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 22 of 27
R2A20121SP
Error Amplifier Offset Voltage vs. Ambient Temperature Characteristics
10.0 8.0 6.0 4.0 2.0
Vos
[mV]
0.0 -2.0 -4.0 -6.0
-40 -25 0 25 Ta 50 [C] 75 100 125
Error Amplifier Source Current vs. Ambient Temperature Characteristics
-100
FB (+) = 1.25 V, FB (-) = 0.75 V, COMP = 2 V
-200
ISOURCE
[A]
-300
-400
-500
-600
-700 -40
-25
0
25 Ta
50 [C]
75
100
125
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 23 of 27
R2A20121SP
Error Amplifier Sink Current vs. Ambient Temperature Characteristics
20 18 16 14
FB (+) = 1.25 V, FB (-) = 1.75 V, COMP = 2 V
[mA] ISINK
12 10 8 6 4 2
0
-40 -25 0 25 Ta 50 [C] 75 100 125
Soft-start Pin Current vs. Ambient Temperature Characteristics
-5 -6 -7 -8
SS = 1 V
[A] Iss
-9 -10 -11 -12 -13 -14 -15
-40 -25
0
25 Ta
50 [C]
75
100
125
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 24 of 27
R2A20121SP
Switching Frequency vs. Ambient Temperature Characteristics
580 560 540 520
fsw [kHz]
500 480 460 440 420 400 380 -40
-25
0
25 Ta
50 [C]
75
100
125
TD1 Delay vs. Ambient Temperature Characteristics
50
45
40
35
TD1 [ns]
30
25
20
15 -40
-25
0
25 Ta
50 [C]
75
100
125
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 25 of 27
R2A20121SP
Current Sense Delay Time vs. Ambient Temperature Characteristics 70
60
50
Tpd [ns]
40
30
20
10
0 -40
-25
0
25 Ta
50 [C]
75
100
125
Overcurrent Protection Delay Time vs. Ambient Temperature Characteristics
100
80
[ns] Tpd_cs
60
40
20
0
-40
-25
0
25
50
75
100
125
Ta
[C]
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 26 of 27
R2A20121SP
Package Dimensions
JEITA Package Code P-TSSOP20-4.4x6.5-0.65 RENESAS Code PTSP0020JB-A Previous Code TTP-20DAV MASS[Typ.] 0.07g
*1
D F 11
20
NOTE) 1. DIMENSIONS"*1 (Nom)"AND"*2" DO NOT INCLUDE MOLD FLASH. 2. DIMENSION"*3"DOES NOT INCLUDE TRIM OFFSET.
bp
HE
*2
E
Index mark
Terminal cross section ( Ni/Pd/Au plating )
Reference Dimension in Millimeters Symbol
c
1 Z e
*3
10 bp L1 x M
A1
L
y
Detail F
D E A2 A1 A bp b1 c c1 HE e x y Z L L1
Min Nom Max 6.50 6.80 4.40
0.03 0.07 0.10 1.10 0.15 0.20 0.25 0.10 0.15 0.20 0 8 6.20 6.40 6.60 0.65 0.13 0.10 0.65 0.4 0.5 0.6 1.0
REJ03D0914-0100 Rev.1.00 Sep 29, 2008 Page 27 of 27
A
Sales Strategic Planning Div.
Nippon Bldg., 2-6-2, Ohte-machi, Chiyoda-ku, Tokyo 100-0004, Japan
Notes: 1. This document is provided for reference purposes only so that Renesas customers may select the appropriate Renesas products for their use. Renesas neither makes warranties or representations with respect to the accuracy or completeness of the information contained in this document nor grants any license to any intellectual property rights or any other rights of Renesas or any third party with respect to the information in this document. 2. Renesas shall have no liability for damages or infringement of any intellectual property or other rights arising out of the use of any information in this document, including, but not limited to, product data, diagrams, charts, programs, algorithms, and application circuit examples. 3. You should not use the products or the technology described in this document for the purpose of military applications such as the development of weapons of mass destruction or for the purpose of any other military use. When exporting the products or technology described herein, you should follow the applicable export control laws and regulations, and procedures required by such laws and regulations. 4. All information included in this document such as product data, diagrams, charts, programs, algorithms, and application circuit examples, is current as of the date this document is issued. Such information, however, is subject to change without any prior notice. Before purchasing or using any Renesas products listed in this document, please confirm the latest product information with a Renesas sales office. Also, please pay regular and careful attention to additional and different information to be disclosed by Renesas such as that disclosed through our website. (http://www.renesas.com ) 5. Renesas has used reasonable care in compiling the information included in this document, but Renesas assumes no liability whatsoever for any damages incurred as a result of errors or omissions in the information included in this document. 6. When using or otherwise relying on the information in this document, you should evaluate the information in light of the total system before deciding about the applicability of such information to the intended application. Renesas makes no representations, warranties or guaranties regarding the suitability of its products for any particular application and specifically disclaims any liability arising out of the application and use of the information in this document or Renesas products. 7. With the exception of products specified by Renesas as suitable for automobile applications, Renesas products are not designed, manufactured or tested for applications or otherwise in systems the failure or malfunction of which may cause a direct threat to human life or create a risk of human injury or which require especially high quality and reliability such as safety systems, or equipment or systems for transportation and traffic, healthcare, combustion control, aerospace and aeronautics, nuclear power, or undersea communication transmission. If you are considering the use of our products for such purposes, please contact a Renesas sales office beforehand. Renesas shall have no liability for damages arising out of the uses set forth above. 8. Notwithstanding the preceding paragraph, you should not use Renesas products for the purposes listed below: (1) artificial life support devices or systems (2) surgical implantations (3) healthcare intervention (e.g., excision, administration of medication, etc.) (4) any other purposes that pose a direct threat to human life Renesas shall have no liability for damages arising out of the uses set forth in the above and purchasers who elect to use Renesas products in any of the foregoing applications shall indemnify and hold harmless Renesas Technology Corp., its affiliated companies and their officers, directors, and employees against any and all damages arising out of such applications. 9. You should use the products described herein within the range specified by Renesas, especially with respect to the maximum rating, operating supply voltage range, movement power voltage range, heat radiation characteristics, installation and other product characteristics. Renesas shall have no liability for malfunctions or damages arising out of the use of Renesas products beyond such specified ranges. 10. Although Renesas endeavors to improve the quality and reliability of its products, IC products have specific characteristics such as the occurrence of failure at a certain rate and malfunctions under certain use conditions. Please be sure to implement safety measures to guard against the possibility of physical injury, and injury or damage caused by fire in the event of the failure of a Renesas product, such as safety design for hardware and software including but not limited to redundancy, fire control and malfunction prevention, appropriate treatment for aging degradation or any other applicable measures. Among others, since the evaluation of microcomputer software alone is very difficult, please evaluate the safety of the final products or system manufactured by you. 11. In case Renesas products listed in this document are detached from the products to which the Renesas products are attached or affixed, the risk of accident such as swallowing by infants and small children is very high. You should implement safety measures so that Renesas products may not be easily detached from your products. Renesas shall have no liability for damages arising out of such detachment. 12. This document may not be reproduced or duplicated, in any form, in whole or in part, without prior written approval from Renesas. 13. Please contact a Renesas sales office if you have any questions regarding the information contained in this document, Renesas semiconductor products, or if you have any other inquiries.
RENESAS SALES OFFICES
Refer to "http://www.renesas.com/en/network" for the latest and detailed information. Renesas Technology America, Inc. 450 Holger Way, San Jose, CA 95134-1368, U.S.A Tel: <1> (408) 382-7500, Fax: <1> (408) 382-7501 Renesas Technology Europe Limited Dukes Meadow, Millboard Road, Bourne End, Buckinghamshire, SL8 5FH, U.K. Tel: <44> (1628) 585-100, Fax: <44> (1628) 585-900 Renesas Technology (Shanghai) Co., Ltd. Unit 204, 205, AZIACenter, No.1233 Lujiazui Ring Rd, Pudong District, Shanghai, China 200120 Tel: <86> (21) 5877-1818, Fax: <86> (21) 6887-7858/7898 Renesas Technology Hong Kong Ltd. 7th Floor, North Tower, World Finance Centre, Harbour City, Canton Road, Tsimshatsui, Kowloon, Hong Kong Tel: <852> 2265-6688, Fax: <852> 2377-3473 Renesas Technology Taiwan Co., Ltd. 10th Floor, No.99, Fushing North Road, Taipei, Taiwan Tel: <886> (2) 2715-2888, Fax: <886> (2) 3518-3399 Renesas Technology Singapore Pte. Ltd. 1 Harbour Front Avenue, #06-10, Keppel Bay Tower, Singapore 098632 Tel: <65> 6213-0200, Fax: <65> 6278-8001 Renesas Technology Korea Co., Ltd. Kukje Center Bldg. 18th Fl., 191, 2-ka, Hangang-ro, Yongsan-ku, Seoul 140-702, Korea Tel: <82> (2) 796-3115, Fax: <82> (2) 796-2145
http://www.renesas.com
Renesas Technology Malaysia Sdn. Bhd Unit 906, Block B, Menara Amcorp, Amcorp Trade Centre, No.18, Jln Persiaran Barat, 46050 Petaling Jaya, Selangor Darul Ehsan, Malaysia Tel: <603> 7955-9390, Fax: <603> 7955-9510
(c) 2008. Renesas Technology Corp., All rights reserved. Printed in Japan.
Colophon .7.2

▲Up To Search▲

Price & Availability of R2A20121SP

	To Download R2A20121SP Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .