AAT2805

Dual High Efficiency Charge Pump for White LED and Flash Applications General Description The AAT2805 is a dual charge pump designed to support both the white LED backlight and flash applications for systems operating with lithium-ion/polymer batteries. The backlight charge pump is capable of driving up to four LEDs at a total of 120mA. The current sinks may be operated individually or in parallel for driving higher current LEDs. To maximize power efficiency, the charge pump operates in 1X, 1.5X, or 2X mode, where the mode of operation is automatically selected by comparing the forward voltage of each LED with the input voltage. AnalogicTech's AS2Cwire™ (Advanced Simple Serial Control™) serial digital input is used to enable, disable, and set current for each LED with a 16-level logarithmic scale plus four low-current settings down to 50µA for optimized efficiency, with a typical operating quiescent current of less than 50µA. The flash charge pump is a charge pump doubler with a regulated output voltage. It is designed to deliver 120mA of continuous current and up to 250mA of pulsed current. It has an independent enable pin for improved power savings. The AAT2805 has thermal protection and built-in soft-start circuitry. A low-current shutdown feature disconnects the load from VIN and reduces quiescent current to less than 1µA. The AAT2805 is available in a Pb-free, space-saving, thermally-enhanced TDFN44-16 package and is rated over the -40°C to +85°C temperature range. AAT2805 Features • • • ChargePump™ • • • • • • VIN Range: 2.7V to 5.5V Dual Charge Pump to Support Backlight and Flash LEDs Backlight Charge Pump: — Regulated Current — Four Current Sink Inputs — AS2Cwire Brightness Control — Tri-Mode Charge Pump — Maximum 30mA of Current Per Input — Low IQ (50µA) in Light Load Mode Flash Charge Pump: — Regulated Output Voltage — Up to 250mA of Pulsed Current Independent Backlight/Flash Control Low Noise 1MHz Constant Frequency Operation Automatic Soft-Start No Inductors Available in TDFN44-16 Package Applications • • • Color (RGB) Lighting White LED Backlighting White LED Photo Flash Typical Application C1 1μF C2 1μF C3 1μF C1+ C1- C2+ C2- C3+ C3VOUT_FL VIN VIN CIN 1 μF COUT 1μF VOUT_FLASH Flash AAT2805 VOUT_BL Backlight D1 EN/SET EN_FLSH EN/SET EN_FLSH GND D1 D2 D3 D4 D2 D3 D4 COUT 1μF 2805.2006.04.1.7 1 Dual High Efficiency Charge Pump for White LED and Flash Applications Pin Descriptions Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 EP AAT2805 Symbol C3C3+ VOUT_FL VIN D4 D3 D2 D1 GND EN/SET C1+ C1VOUT_BL C2+ C2EN_FLSH Function Flying capacitor 3 negative terminal. Flying capacitor 3 positive terminal. Connect a 1µF capacitor between C3+ and C3-. Regulated output voltage for flash LED. Requires 1µF capacitor connected between this pin and ground. Input power supply. Requires 1µF capacitor connected between this pin and ground. Current sink input 4. Current sink input 3. Current sink input 2. Current sink input 1. Ground. AS2Cwire serial interface control pin. It is used to enable/disable the backlight charge pump and to control the brightness of the white LEDs. Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-. Flying capacitor 1 negative terminal. Regulated output voltage for white LED. Requires 1µF capacitor connected between this pin and ground. Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-. Flying capacitor 2 negative terminal. Enable/disable pin for the flash charge pump. Exposed paddle (bottom); connect to GND directly beneath package. Pin Configuration TDFN44-16 (Top View) C3C3+ VOUT_FL VIN D4 D3 D2 D1 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 EN_FLSH C2C2+ VOUT_BL C1C1+ EN/SET GND 2 2805.2006.04.1.7 Dual High Efficiency Charge Pump for White LED and Flash Applications Absolute Maximum Ratings1 Symbol VIN VEN/SET; EN_FL TLEAD AAT2805 Description Input Voltage EN/SET; EN_FL to GND Voltage Maximum Soldering Temperature (at leads, 10 sec) Value -0.3 to 6.0 -0.3 to VIN + 0.3 300 Units V V °C Thermal Information2 Symbol PD θJA Description Maximum Power Dissipation Maximum Thermal Resistance 3 Value 2.0 50 Units W °C/W 1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 2. Mounted on an FR4 board. 3. Derate 6.25mW/°C above 25°C. 2805.2006.04.1.7 3 Dual High Efficiency Charge Pump for White LED and Flash Applications Electrical Characteristics1 VIN = 3.6V; CIN = COUT = C1 = C2 = C3 = 1.0µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol VIN AAT2805 Description Operation Range Conditions Min Typ Max Units 2.7 5.5 1 3.0 3.0 µA 4.5 1.0 10 0.5 4.32 4.3 120 250 100 1.0 0.4 1.4 0.3 50 75 500 500 -1.0 1.0 75 7 4.5 4.5 4.68 4.7 V mA µA % % Ω V Input Power Supply ICC Operating Current ISHDN IDX I(D-Match) RSINK VOUT_FL IOUT_FL TSS FCLK VEN(L) VEN(H) TEN/SET LO TEN/SET_HI_MIN TEN/SET_HI_MAX TOFF TLAT II Shutdown Current Input Current Accuracy2, 3 Current Matching Between VD1:D4 = 3.6, VIN = 3.5V Any Two Current Sink Inputs2, 4 Sink Switch Impedance (each)2 3.0V < VIN < 5V, IOUT = 100mA; Flash Charge Pump Output EN_FLSH = VIN 3.0V < VIN < 5V, IOUT = 150mA; Voltage5 EN_FLSH = VIN Maximum Continuous IOUT5 VIN = 3.6V; VOUT = 4.5V; EN_FLSH = VIN Maximum Pulsed IOUT5 VIN = 3.6V; VOUT = 4.5V; IPULSED < 500ms Soft-Start Time Clock Frequency Enable Threshold Low Enable Threshold High EN/SET Low Time VEN/SET < 0.6V Minimum EN/SET High Time VEN/SET > 1.4V Maximum EN/SET High Time EN/SET Off Timeout6 VEN/SET < 0.6V EN/SET Latch Timeout7 VEN/SET > 1.4V Enable and EN/SET Input VEN/SET = VEN_FLSH = VIN Leakage 1X Mode, 3.0 ≤ VIN ≤ 5.5, Active, No Load Current; EN_FLSH = GND, EN/SET = VIN 1.5X Mode, 3.0 ≤ VIN ≤ 5.5, Active, No Load Current; EN_FLSH = GND, EN/SET = VIN 2X Mode, 3.0 ≤ VIN ≤ 5.5, Active, No Load Current; EN_FLSH = GND, EN/SET = VIN EN_FLSH = GND, 50µA Output Setting, 1X Mode 3.0 ≤ VIN ≤ 5.5, No Load Current; EN_FLSH = VIN, EN/SET = GND EN_FLSH = EN/SET = 0 ISET = 30mA; TA = 25°C 0.3 1.0 1.0 50 2.0 mA -10 mA µs MHz V V µs ns µs µs µs µA 1. The AAT2805 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 2. Specification applies only to the tri-mode charge pump. 3. Determined by the average of all active channels. 4. Current matching is defined as the deviation of any sink current from the average of all active channels. 5. Specification applies only to the charge pump doubler. 6. The EN/SET pin must remain logic low (less than VEN(L)) for the duration of longer than 500µs to guarantee the off timeout. 7. The EN/SET pin must remain logic high (greater than VEN(H)) for the duration of longer than 500µs to guarantee the latch timeout. 4 2805.2006.04.1.7 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics–Flash Driver Charge Pump Section Output Voltage vs. Output Current (VOUT_FL = 4.5V; EN_FL = VIN; EN/SET = GND) 4.60 AAT2805 Maximum Current Pulse vs. Supply Voltage (VOUT_FL = 4.5V; EN_FL = VIN; EN/SET = GND) Maximum Current Pulse (mA) 450 400 350 300 250 200 150 100 50 Output Voltage (V) 4.56 4.52 4.48 4.44 One-shot pulse duration = 250ms VOUT > 4.0V 3.6V 3.0V 2.7V 3.3V 4.40 0.1 1.0 10.0 100.0 1000.0 0 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 Output Current (mA) Supply Voltage (V) Start-Up Time (50mA Load) Start-Up Time (100mA Load) EN_FLSH (1V/div) EN_FLSH (1V/div) VOUT_FL (1V/div) VOUT_FL (1V/div) TIme (100µs/div) TIme (100µs/div) Load Response vs. Time (50mA Load) VIN = 3.5V VOUT_FL (10mV/div) VOUT_FL (10mV/div) Load Response vs. Time (100mA Load) VIN = 3.5V IOUT (20mA/div) IOUT (50mA/div) Time (5ms/div) Time (5ms/div) 2805.2006.04.1.7 5 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics–Flash Driver Charge Pump Section Output Ripple Voltage vs. Time (IOUT = 50mA @ VIN = 3.5V) VIN (10mV/div) VOUT (10mV/div) VIN (10mV/div) VOUT (20mV/div) AAT2805 Output Ripple Voltage vs. Time (IOUT = 100mA @ VIN = 3.5V) IIN (10mA/div) IIN (10mA/div) Time (500ns/div) Time (500ns/div) Supply Current vs. Supply Voltage IOUT = 0μA C3 = 1μF VEN_FL = VIN Oscillator Frequency vs. Supply Voltage Oscillator Frequency (MHz) 1.30 3.00 Supply Current (mA) 2.75 2.50 2.25 2.00 1.75 1.50 1.25 1.00 2.5 1.25 +25°C 1.20 +85°C -40°C 1.15 3.0 3.5 4.0 4.5 5.0 1.10 2.7 3.2 3.7 4.2 4.7 Supply Voltage (V) Supply Voltage (V) 6 2805.2006.04.1.7 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics–White LED Backlight Driver Section Turn-On to 1X Mode (VIN = 4.2V; 20mA Load) AAT2805 Turn-On to 1.5X Mode (VIN = 3.5V; 20mA Load) EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div) Time (100µs/div) EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div) Time (100µs/div) Turn-On to 2X Mode (VIN = 2.8V; 20mA Load) EN (2V/div) VF (1V/div) Turn-Off from 1.5X Mode (VIN = 3.5V; 20mA Load) EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div) IIN (100mA/div) Time (100µs/div) Time (500µs/div) Efficiency vs. Supply Voltage 100 90 80 4.1mA VF = 2.9V 20.4 20.2 Current Matching vs. Temperature Channel 2 Channel 4 Channel 3 Channel 1 Efficiency (%) 70 60 50 40 30 20 10 0 2.6 2.8 2.9 3.1 3.2 3.4 3.6 3.7 3.9 4.0 4.2 1mA VF = 2.7V 10.2mA VF = 3.1V 20mA VF = 3.4V Current (mA) 20.0 19.8 19.6 19.4 19.2 19.0 -40 -20 0 20 40 60 80 Supply Voltage (V) Temperature (°C) 2805.2006.04.1.7 7 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics–White LED Backlight Driver Section Load Characteristics (VIN = 3.7V; 1.5X Mode; 15mA Load) AAT2805 Load Characteristics (VIN = 2.7V; 2X Mode; 15mA Load) VIN (40mV/div) CP (40mV/div) VSINK (40mV/div) VIN (40mV/div) CP (40mV/div) VSINK (40mV/div) Time (500ns/div) Time (500ns/div) Load Characteristics (VIN = 3.9V; 1.5X Mode; 20mA Load) Load Characteristics (VIN = 2.9V; 2X Mode; 20mA Load) VIN (40mV/div) CP (40mV/div) VSINK (40mV/div) VIN (40mV/div) CP (40mV/div) VSINK (40mV/div) Time (500ns/div) Time (500ns/div) Load Characteristics (VIN = 4.2V; 1.5X Mode; 30mA Load) VIN (40mV/div) CP (40mV/div) Load Characteristics (VIN = 3.2V; 2X Mode; 30mA Load) VIN (40mV/div) CP (40mV/div) VSINK (40mV/div) VSINK (40mV/div) Time (500ns/div) Time (500ns/div) 8 2805.2006.04.1.7 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics–White LED Backlight Driver Section EN/SET Latch Timeout vs. Input Voltage EN/SET Latch Timeout (μs) 350 400 AAT2805 EN/SET Off Timeout vs. Input Voltage EN/SET Off Timeout (μs) 300 250 200 150 100 50 0 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 350 300 250 200 150 100 50 0 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 -40°C -40°C 25°C 85°C 25°C 85°C Input Voltage (V) Input Voltage (V) Input Ripple vs. Input Voltage Enable Threshold High (V) 18 16 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 Enable Threshold High vs. Input Voltage Amplitude (mV) 14 12 10 8 6 4 2 0 2.50 2.67 2.84 3.01 3.18 3.35 3.52 3.69 3.86 4.03 4.20 -40°C 20mA 30mA 25°C 85°C 10.2mA 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 Input Voltage (V) Input Voltage (V) Enable Threshold Low vs. Input Voltage Enable Threshold Low (V) 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 -40°C 25°C 85°C Input Voltage (V) 2805.2006.04.1.7 9 Dual High Efficiency Charge Pump for White LED and Flash Applications Functional Block Diagram C3+ Soft-Start AAT2805 C3- EN_FLSH 1MHz Oscillator 2X Charge Pump VOUT_FLSH VIN VREF Soft-Start Control 1MHz Oscillator Voltage Reference 1X 1.5X 2X Charge Pump C1+ C1C2+ C2VOUT_BL D/A 6 X 16 Bit ROM D/A D/A D1 D2 D3 D4 GND EN/SET Control Logic 6 X 16 Bit ROM D/A Functional Description The AAT2805 is a dual charge pump designed for flash and white LED applications. The backlight charge pump is a tri-mode load switch (1X) and high efficiency (1.5X or 2X) charge pump device. To maximize power conversion efficiency, an internal sensing circuit monitors the voltage required on each constant current sink input and sets the load switch and charge pump modes based on the input battery voltage and the current sink input voltage. As the battery voltage discharges over time, the white LED charge pump is enabled when any of the four current sink inputs near dropout. The charge pump initially starts in 1.5X mode. If the charge pump output drops enough for any current source output to become close to dropout, the charge pump will automatically transition to 2X mode. The four constant current sink inputs D1 to D4 can drive four individual LEDs with a maximum current of 30mA per LED. The unused sink inputs must be connected to VOUT_BL; otherwise, the part will operate only in 2X charge pump mode. The AS2Cwire serial interface enables and sets the constant current sink magnitudes. AS2Cwire addressing allows the LED main channels D1-D3 to be controlled independently from the LED sub-channel D4. The flash charge pump is a charge pump doubler with regulated output voltage. It is designed to deliver 120mA of continuous current and 250mA of pulsed current. 10 2805.2006.04.1.7 Dual High Efficiency Charge Pump for White LED and Flash Applications The AAT2805 requires six external components: three 1µF ceramic capacitors for the charge pump flying capacitors (C1, C2, and C3), one 1µF ceramic input capacitor (CIN), one 0.33µF to 1µF ceramic capacitor for backlight charge pump output capacitor (COUT), and one 1µF ceramic capacitor for flash charge pump output capacitor (COUT). Max IOUT (mA) 30mA 15mA 30.0 26.7 23.8 21.4 19.0 16.7 15.2 13.3 11.9 10.5 9.5 8.6 7.6 6.7 6.2 0.0 15.0 13.3 11.9 10.7 9.5 8.3 7.6 6.7 6.0 5.2 4.8 4.3 3.8 3.3 3.1 0.0 AAT2805 Data 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20mA 20.0 17.8 15.9 14.3 12.7 11.1 10.2 8.9 7.9 7.0 6.3 5.7 5.1 4.4 4.1 0.0 Constant Current Output Level Settings The constant current level for the LED channels is set via the AS2Cwire serial interface according to a logarithmic scale. The current level spacing is 1dB between adjacent constant current settings. In this manner, LED brightness appears to change linearly when the settings are traversed. Because the inputs D1 to D4 are true independent constant current sinks, the voltage observed on any single given input will be determined by the difference between VOUT and the actual forward voltage (VF) of the LED being driven. Since the constant current levels are programmable, no PWM (pulse width modulation) or additional control circuitry is needed to control LED brightness. This feature greatly reduces the burden on a microcontroller or system IC to manage LED or display brightness, allowing the user to "set it and forget it." With its high-speed serial interface (>1MHz data rate), the LED current drive can be changed successively to brighten or dim LEDs, in smooth transitions (e.g., to fade-out) or in abrupt steps, giving the user complete programmability and real-time control of LED brightness. For each Max Current scale (see Table 1), there are 16 current level settings separated from one another by approximately 1dB. Code 1 is full-scale current and Code 15 is full-scale current attenuated by roughly 14dB. Code 16 is reserved as a "no current" setting. When programming the charge pump, it will default to the 20mA maximum scale. The AAT2805 offers an additional Low Current mode with reduced quiescent current (see Table 2). This mode is especially useful for low-current applications where a continuous, low-current state is maintained. The reduction in quiescent current significantly reduces the impact due to maintaining a continuous backlighting state. Table 1: Constant Current Programming Levels. Data 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 D1-D3 (mA) 0 0 0 0 0 0 0 0 0.05 0.5 1 2 0.05 0.5 1 2 D4 (mA) 0 0 0 0 0.05 0.5 1 2 0 0 0 0 0.05 0.5 1 2 Table 2: Low Current Register Settings. 2805.2006.04.1.7 11 Dual High Efficiency Charge Pump for White LED and Flash Applications AS2Cwire Serial Interface The AS Cwire single wire interface is used to set the possible combinations of current levels and LED channel states. AS2Cwire has addressing capability for multiple data registers. With multiple data registers, the main and sub-channel can be programmed together or independently from one another. AS2Cwire relies on the number of rising edges of the EN/SET pin to address and load the registers. AS2Cwire latches data or address after the EN/SET pin has been held high for time TLAT. Address or data is differentiated by the number of EN/SET rising edges. Since the data registers are 4 bits each, the differentiating number of pulses is 24 or 16, so that Address 1 is signified by 17 rising edges, Address 2 by 18 rising edges, and so forth. Data is set to any number of rising edges between 1 and including 16. A typical write protocol is a burst of EN/SET rising edges, signifying a particular address, followed by a pause with EN/SET held high for the TLAT timeout period, a burst of rising edges signifying data, and a TLAT timeout for the data registers. Once an address is set, then multiple writes to the corresponding data register are allowed. 2 AAT2805 the part is programmed to operate in Low Current mode and the Data for Addresses 1-3 is irrelevant. In Low Current mode, the Low Current register takes precedence. See the Low Current Register Settings table below for the current level settings and main/ sub-configurations that result. Address 1 2 3 4 5 EN/SET Edges 17 18 19 20 21 Addressed Register 1&2: D1-D4 Current 1: D1-D3 Current 2: D4 Current 3: Max Current 4: Low Current Table 3: Address Settings. Max Current and Low Current Registers Use the Max Current and Low Current registers to program constant current settings outside of the 20mA Max scale. By default (without changing the Max Current register), the charge pump operates in the 20mA Max scale (see Table 1). For example, to change to the 30mA Max scale, address the Max Current register with 20 rising edges and pause for TLAT. Program the Max Current register with 2 rising edges and pause for TLAT. The part will next operate in the same Data row, but for the setting found in the 30mA Max column. Next, to change to a different setting on the 30mA Max scale, address the D1-D4 register with 17 rising edges. Program the new constant current level with 1-16 rising edges. The part will update to the new Data setting as shown in Table 1. The charge pump has a distinct Low Current mode with ultra-low quiescent current. For drive currents of 2mA or less, the part operates with significantly reduced quiescent current. This is particularly useful for applications requiring an "always on" condition such as transmissive displays. For another example, to change to Low Current mode, address the Max Current register with 20 rising edges and pause for TLAT. Program the Max Current register with 4 rising edges and pause for TLAT. Address the Low Current register with 21 rising edges and pause for TLAT. Program the Low Current register with 1-16 rising edges. The part will update to the new Low Current mode setting and operate with significantly reduced quiescent current. When EN/SET is held low for an amount of time greater than TOFF, the charge pump enters into shutdown mode and draws less than 1µA from the supply. Address 1 is the default address on the first rising edge after the charge pump has been disabled. Whenever shutdown mode is entered, all registers are reset to 1. AS2Cwire Addressing Five addresses are available to enable all of the part's functionality (see Table 3). Two 4-bit registers control the main and sub-channel, giving 16 settings for each. The main and sub-channel are programmed to the same constant current level by using Address 1. Use Addresses 2 and 3 to program the main and sub-channel independently. Use Address 4 to program the Max Current register, which sets the Max Current scale. Lastly, Address 5 programs the Low Current register. The Low Current register controls the efficient Low Current mode. When the Max Current register is programmed to 1, 2, or 3, changing the data for Addresses 1-3 will result in the corresponding values found in Table 1. When the Max Current register is programmed to 4, 12 2805.2006.04.1.7 Dual High Efficiency Charge Pump for White LED and Flash Applications AS2Cwire Serial Interface Timing Diagram Address THI TLO TLAT TLAT AAT2805 Data EN/SET 1 2 17 18 1 2... n