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High Efficiency Synchronous
a
Step-Down Switching Regulators
ADP1148, ADP1148-3.3, ADP1148-5
FUNCTIONAL BLOCK DIAGRAM
FEATURES
Operation From 3.5 V to 18 V Input Voltage
Ultrahigh Efficiency > 95%
ADJUSTABLE
VERSION
PWR SIGNAL
Low Shutdown Current
V P-DRIVE N-DRIVE GND GND SENSE(+) V SENSE(–)
IN FB
Current Mode Operation for Excellent Line and Load
3 1 14 12 11 8 9
7
Transient Response
ADP1148
High Efficiency Maintained Over Wide Current Range
NON-OVERLAP
Logic Controlled Micropower Shutdown DRI
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ADP1148, ADP1148-3.3, ADP1148-5–SPECIFICATIONS 1 (08C ≤ T ≤ +708C, V = 10 V, V = 0 V, unless otherwise noted. See Figure 17.) ELECTRICAL CHARACTERISTICS A IN SHUTDOWN 2 Parameter Symbol Conditions Min Typ Max Units FEEDBACK VOLTAGE ADP1148 Only V V = 9 V 1.21 1.25 1.29 V 10 IN FEEDBACK CURRENT ADP1148 Only I 0.2 1.0 μA 10 REGULATED OUTPUT VOLTAGE V V = 9 V OUT IN ADP1148-3.3 I = 700 mA 3.23 3.33 3.43 V LOAD ADP1148-5 I = 700 mA 4.9 5.05 5.2 V LOAD = +25°C, V = 7 V to 12 V, OUTPUT VOLTAGE LINE T
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ADP1148, ADP1148-3.3, ADP1148-5 1 ELECTRICAL CHARACTERISTICS (–408C ≤ T ≤ +858C, V = 10 V, V = 0 V, unless otherwise noted. See Figure 17.) A IN SHUTDOWN 2 Parameter Symbol Conditions Min Typ Max Units FEEDBACK VOLTAGE ADP1148 Only V V = 9 V 1.20 1.25 1.30 V 10 IN REGULATED OUTPUT VOLTAGE V V = 9 V OUT IN ADP1148-3.3 I = 700 mA 3.17 3.33 3.4 V LOAD ADP1148-5 I = 700 mA 4.85 5.05 5.2 V LOAD 3 INPUT DC SUPPLY CURRENT I Q Normal Mode V = 4 V < V < 18 V 1.6 2.6 mA IN IN Sleep Mode (ADP1148-3) V = 4
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ADP1148, ADP1148-3.3, ADP1148-5 PIN FUNCTION DESCRIPTIONS Pin # Mnemonic Function 1 P-Channel Drive High Current Gate Drive for Top P-Channel MOSFET. The voltage swing at Pin 4 is from V to IN ground. 2 NC No Connection. Input Voltage. 3V IN External Capacitor C from Pin 4 to Ground Sets the Operating Frequency. The frequency is also 4C T T /V . dependent on the ratio V OUT IN Internal Supply Voltage, Nominally 3.3 V. Must be decoupled to signal ground. Do not externally load 5 Int V CC this pin
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Typical Performance Characteristics–ADP1148, ADP1148-3.3, ADP1148-5 200 1000 1000 V = V = 5V SENSE OUT L = 50mH 800 800 R = 0.02V SENSE 150 L = 25mH 600 R = 0.02V 600 SENSE 100 400 400 V = 12V IN 50 V = 7V L = 50mH IN 200 R = 0.05V SENSE V = 10V 200 IN 0 0 5 0 123 4 0 0 100 200 300 05 1 234 FREQUENCY – kHz MAXIMUM OUTPUT CURRENT – A (V –V ) VOLTAGE – V IN OUT Figure 3. Selecting R vs. Maxi- Figure 4. Operating Frequency vs. Figure 5. Selecting Minimum Output SENSE mum Output Current Timing Capac
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ADP1148, ADP1148-3.3, ADP1148-5–Typical Performance Characteristics 1.8 80 30 1.6 08C 70 25 1.4 60 258C 1.2 20 50 708C Qn+Qp = 100nC 1.0 15 40 0.8 30 10 0.6 5V Qn+Qp = 50nC 20 0.4 5 3.3V 10 0.2 0 0.0 0 20 50 80 110 140 170 200 230 260 12 468 10 12 0.3 0.5 1.0 1.5 2.0 2.5 3.0 3.3 3.5 4.0 4.5 5.0 OPERATING FREQUENCY – kHz (V –V ) – V OUTPUT VOLTAGE – V IN OUT Figure 13. Gate Charge Supply Figure 14. Off Time vs. V Figure 12. Operating Frequency vs. OUT Current (V –V ) IN OUT 155 150 145 MAXIMUM TH
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ADP1148, ADP1148-3.3, ADP1148-5 APPLICATIONS To prevent both the external MOSFETs from ever being turned The ADP1148 uses a current-mode, constant off-time structure on simultaneously, feedback is incorporated to sense the state of to switch a pair of external complementary N- and P-channel the driver output pins. MOSFETs. The operating frequency of the device is deter- Before the N drive output can go high, the P drive output must mined by the value of the external capacitor connected to the al
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ADP1148, ADP1148-3.3, ADP1148-5 As the operating frequency is increased, the gate charge losses components are also available from Coiltronics which do not will cause reduced efficiency (see Efficiency section). The full increase the component height significantly. formula for operating frequency is given by: Power MOSFET f = ( 1 – V /V )/t OUT IN OFF Two external power MOSFETs must be selected for use with 4 the ADP1148, a P-channel MOSFET for the main switch, and where t = 1.3 × 10 × C × V /V
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ADP1148, ADP1148-3.3, ADP1148-5 An additional 0.1 μF – 1 μF ceramic bypass capacitor is advised Although all dissipative elements in the circuit produce losses, on V Pin 3 parallel with C . The selection of C is driven three main sources usually account for most of the losses in IN IN OUT by the required effective series resistance (ESR). The ESR of ADP1148 circuits: C must be less than twice the value of R for proper 1) ADP1148 dc bias current, OUT SENSE operation of the ADP1148: 2) MOSFET gate
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ADP1148, ADP1148-3.3, ADP1148-5 Design Example Output Crowbar As a design example, assume V = 12 V (nominal), V = 5 V, An added feature to using an N-channel MOSFET as the syn- IN OUT I = 2 A, and f = 200 kHz, R . C , and L can immedi- chronous switch is the ability to crowbar the output with the MAX SENSE T ately be calculated: same MOSFET. Pulling the timing cap C pin above 1.5 V T when the output voltage is greater than the desired regulated R = 100 mV/2 = 50 mΩ SENSE value will turn “on” t
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ADP1148, ADP1148-3.3, ADP1148-5 Board Layout 4) Does the (+) plate of C connect to the source of the IN When laying out the printed circuit board, the following check P-channel MOSFET as closely as possible? This capacitor list should be used to ensure proper operation of the ADP1148. provides the ac current to the P-channel MOSFET. These items are also illustrated graphically in the layout diagram 5) Is the input decoupling capacitor (1 μF) connected closely of Figure 18. Check the following in
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ADP1148, ADP1148-3.3, ADP1148-5 V IN 4V TO 18V C IN IRF7204 D1 100mF 10BQ040 20V IRF7403 1 14 P-DRIVE N-DRIVE 13 2 *L NC NC 1mF 50mH ADP1148-3.3 12 3 POWER GND V IN 4 11 C SIGNAL GND T C T 5 10 300pF INT V SHUTDOWN CC 10nF 6 9 C OUT I V TH FB C 220mF C 7 8 10V 3 2 3300pF SENSE(–) SENSE(+) AVX **R 1000pF SENSE R C 0.1V 1kV V OUT 3.3V/1A NC = NO CONNECT *COILTRONICS CTX50-2-MP **KRL SP-1/2-A1-0R100J Figure 19. ADP1148 Low Dropout, 3.3 V/1 A High Efficiency Regulator V IN 4V TO 9V C IN IRF7204 D
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ADP1148, ADP1148-3.3, ADP1148-5 V IN 5.2V TO 14V C IN IRF7204 D1 100mF 10BQ040 20V IRF7403 14 1 N-DRIVE P-DRIVE 13 2 *L NC ADP1148 NC VN2222LL 1mF 50mH 12 3 0V: V = 3.3V OUT V POWER GND IN 5V: V = 5V OUT 4 11 C SIGNAL GND T C T 10 R1A R1B 5 390pF 100pF INT V SHUTDOWN 33kV 43kV CC 1% 1% C OUT 10nF 6 9 220mF I V TH FB 10V 3 2 C C R2 7 8 OS-CON 56kV 3300pF SENSE(–) SENSE(+) 1% **R R 1000pF SENSE C 0.05V V 1kV OUT 3.3V/2A OR 5V/2A NC = NO CONNECT *COILTRONICS CTX50-2-MP **KRL SL-1-C1-0R050J Figur
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ADP1148, ADP1148-3.3, ADP1148-5 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 14-Lead Plastic DIP (N-14) 0.795 (20.19) 0.725 (18.42) 14 8 0.280 (7.11) 0.240 (6.10) 17 0.325 (8.25) 0.195 (4.95) 0.300 (7.62) 0.060 (1.52) 0.115 (2.93) PIN 1 0.015 (0.38) 0.210 (5.33) MAX 0.130 0.160 (4.06) (3.30) MIN 0.115 (2.93) 0.015 (0.381) SEATING 0.022 (0.558) 0.100 0.070 (1.77) 0.008 (0.204) PLANE (2.54) 0.014 (0.356) 0.045 (1.15) BSC 14-Lead Plastic SO (SO-14) 0.3444 (8.75) 0.3367 (8.55) 14 8 0.1574
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–16– PRINTED IN U.S.A. C2219a–2–12/97
