《LDO-DCDC-Charge-Pump的原理比較與不同之處》由會員分享，可在線閱讀，更多相關《LDO-DCDC-Charge-Pump的原理比較與不同之處（43頁珍藏版）》請在裝配圖網上搜索。
1、 Voltage regulator Simcom Hardware Dept.2 wangtao AgendaVoltage regulator presentation: AC-AC DC-AC DC-DC AgendaDC-DC Voltage regulator presentation: LDO Charge pump (inductor less DC-DC) DC-DC (inductor) LDO LDO ( Low Dropout) LDO is a linear regulator Dropout voltage output voltage within 100mV, (
2、Vin Vout) min LDO LDOWorking principle: The voltage divided by resistors R1 PD is limited by package. Compare with step down buck DC-DC, for higher power dissipation or requirements for higher efficiency, recommend buck. Capacitor RequirementsThe output capacitor and especially Equivalent Series Res
3、istance (ESR) are critical for stability. Noise and PSRRSelect an LDO with high power supply rejection ratio (PSRR) for noise immunity from the input supply and low output noise. Some LDO have a bypass (BP) pin for adding capacitance to lower the output noise. LDO parametersCeramic Capacitor Equival
4、ent Circuit Equivalent Series Resistance (ESR) is a critical factor in circuit performance Capacitor Impedance is a function of: Cap Value, ESR and Frequency LDO parametersThings to know about Ceramic Caps:ESR is a function of:Physical size Larger case size caps have lower ESRMaterial TypeX7R Best (
5、lowest ESR)X5R GoodY5V Low cost (highest ESR)Capacitance vs. Frequency:Capacitance value becomes smaller as frequency increases (impedance drops)Again material type has an effect LDO parametersX7R Material MLCCLower ESRLower impedance Better Capacitance vs. FrequencyGood Temp. Tolerance (+/- 10%) Y5
6、V Material MLCCHigher ESRHigher impedancePoor Capacitance vs. FrequencyPoor Temp. Tolerance (+20/- 80%) LDO selection: LOW noise, HIGH PSR No enough PCB area (inductor less) Low voltage drop Low costRegulator Overview Charge PumpTypes of Charge Pump Devices:Types of Charge pump devices are available
7、 in different topologies:Voltage Doubling (2X) Charge Pumps Vout = 2 x VinFractional Charge Pumps Vout = N x Vin, where N = device multiplication Example: Vout = 1.5 x VinRegulated Output Charge Pumps Can be 2x, 3x, Fractional, etc. Voltage Double Charge PumpWorking principle: CONTROL/ CLOCK C+C-V O
8、UTGND VINSHDN S1 S2 S3 S4 Cout Cin CflyVoltage double charge pump block diagram (Vout = 2 x Vin) CIN CFLY COUT S1S4 S3S2VIN V OUT +- +-I CFLYCINVIN + + CIN CFLY COUT S1S4 S3S2VIN V OUT+-+- I CINCFLY COUTVOUTVIN +- +-+- Charge Pump Phase Cycle 1:Charge CFLY Charge Pump Phase Cycle 2:Bootstrap CFLY to
9、 the OutputVoltage Double Charge PumpEquivalent Circuit for Phase Cycle 1: Equivalent Circuit forPhase Cycle 2: Fractional Charge PumpWorking principle: S1S2 S3S4 CFLY1 CFLY2 CIN COUT CONTROL /OSCILLATOR VINV OUT ENABLE Fractional Charge Pumps: Fractional charge pumps offer a technique to multiply a
10、n input voltage by a non-integer multiplication factor Fractional charge pumps can have efficiency advantages in low output voltage applications CIN CFLY2 COUT VOUTVIN +- +-+-CFLY1+-VIN2 VINCIN CFLY2 COUTVOUTVIN +- +-+- CFLY1+- VIN2VIN VIN2 Equivalent Circuit for Phase Cycle 1: Equivalent Circuit fo
11、r Phase Cycle 2:Fraction Charge Pump Works:Operates with 2 switching cycle phases (same as a voltage doubling charge pump)Two “Flying” capacitors are used:In the first switching cycle CFLY1 and CFLY2 are connected in series and placed across Vin, which effects a voltage divider at Vc = Vin/2 for eac
12、h “Fly” capacitor.In the second switching cycle CFLY1 and CFLY2 are connected in parallel, then switched to be in series between Vin and Vout. Vout = Vin + Vin/2 = 1.5 x VinFractional Charge Pump Regulated Charge PumpWorking principle: CONTROL V REF+- GND SHDN S1S2 S3S4VINCin V OUT Cout C+C- Cfly Re
13、gulated Charge Pumps: Regulated charge pumps are voltage doubling, tripling or fractional charge pumps with an output voltage regulation system and feedback control. Regulated charge pumps can provide a stable output voltage from a varied input supply, which is ideal for battery operated devices. Ch
14、arge Pump EfficiencyPrimary items which effect efficiency:RDS(ON) of the MOSFET switching devices-I2R Loss Lower RDS specs are betterOperating quiescent currentVin versus Vout for a given charge pump topology -This applies to regulated charge pumpsTypes of external capacitors used -Cin, Cout and Cfl
15、y Charge Pump EfficiencyEfficiency of Regulated Charge Pumps: Regulated Voltage Doubling Charge PumpsFixed output voltage levelInput voltage may vary with in the device operating rangeThe input voltage is doubled, then regulated down to the desired output voltage. Theoretical Efficiency = = VOUT / 2
16、VINExample: VIN = 2.8V, VOUT = 3.3V, = 58.9% Example: VIN = 3V, VOUT = 4.5V, = 75% Charge Pump EfficiencyEfficiency of Fractional Charge Pumps: Regulated Fractional Charge PumpsFixed output voltage levelInput voltage may vary with in the device operating rangeFractional charge pumps have an advantag
17、e in low voltage applications since the Input to Output difference voltage to be regulated is small. Theoretical Efficiency = = VOUT / 1.5VINExample: VIN = 2.8V, VOUT = 3.3V, = 78.6% Example: VIN = 3V, VOUT = 4.5V, 100% External component selectionExternal Component Selection: Charge pump devices ty
18、pically require 3 to 4 external capacitors depending upon circuit topology. The CIN/COUT to CFLY ratio can range from 1:1 to 10:1 Capacitor value and properties are critical to good charge pump performanceImportant Capacitor Characteristics: Capacitor value Dielectric material type Physical size Cap
19、acitor equivalent series resistance (ESR) Capacitor selection: Ceramic Capacitors are typically the best choice Ceramic capacitors are non-polarized and have low ESR characteristics, typically VOUTHigh Noise and Ripple Low Noise and RippleHigher Power Density SimpleHigher Current Capability IOUT Thermally LimitedHighly design dependant Fast Transient ResponseStep Up or Sep-Down Vin Vout Vin Step Down Only Vout VinRegulator Overview Typical LDO ApplicationTypical DC/DC Switcher Application
LDO-DCDC-Charge-Pump的原理比較與不同之處
