MIC2185 Micrel, Inc. MIC2185 Low Voltage Synchronous Boost PWM Control IC General Description Features Micrels MIC2185 is a high efciency synchronous boost Input voltage range: 2.9V to 14V PWM control IC. With its wide input voltage range of 2.9V to 95% efciency 14V, the MIC2185 can be used to efciently boost voltages Oscillator frequency of 200kHz/400kHz in 1- or 2-cell Li Ion battery powered applications, as well as Frequency sync to 600kHz xed 3.3V and 5V systems. Its powerful 5 output drivers 0.5A shutdown current allow the MIC2185 to supply large output currents with the Two 5 output drivers selection of the proper external MOSFETs. Front edge blanking PWM current mode control With its xed frequency PWM architecture, and easily Cycle-by-cycle current limiting synchronized drive, the MIC2185 is ideal for noise-sensi- Frequency foldback protection tive telecommunications applications. The nominal 400kHz Adjustable under-voltage lockout operating frequency of the MIC2185 can be divided by two, Precision 1.245V reference output allowing the device to be externally synchronized to frequen- 16 pin SOIC narrow body package cies below 400kHz. The MIC2185 also features a low current shutdown mode Applications and a programmable undervoltage lockout. A skipped pulse 3.3V to 5V conversion in telecom systems mode of operation can be manually set to achieve higher Satellite phones efciencies at light load conditions. Cable modems The MIC2185 is available in a 16 pin SOIC package and 16 1-and 2-cell Li Ion battery operated equipment pin QSOP package with an ambient temperature operating range from 40C to 85C. Ordering Information Part Number Junction Frequency Voltage Package Temp. Range Standard Pb-Free MIC2185BM MIC2185YM 200/400kHz Adj 40C to +125C 16-pin SOIC MIC2185BQS MIC2185YQS 200/400kHz Adj 40C to +125C 16-pin QSOP Typical Application 2.4H V = 3.3V Si9803DY (x2) V = 5V IN OUT C IN 1 14 VINA OUTP C OUT 7 16 EN/UVLO VINP 15 6 5V Output Efficiency FREQ/2 FB 100 10 VDD 95 Si4884DY (x2) 4 MIC2185 13 COMP OUTN 8 9 90 VREF CSH 11 85 SYNC 8m 2 12 SKIP PGND 80 SS SGND 3 5 75 V = 3.3V IN 200kHz PWM 70 0 1 2 3 4 5 OUTPUT CURRENT (A) Adjustable Output Synchronous Boost Converter Micrel, Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 MIC2185 Micrel, Inc. Pin Conguration VINA 1 16 VINP SKIP 2 15 FREQ/2 SS 3 14 OUTP COMP 4 13 OUTN SGND 5 12 PGND FB 6 11 SYNC EN/UVLO 7 10 VDD VREF 8 9 CSH 16-pin Narrow Body SOIC (M) 16-pin QSOP (QS) Pin Description Pin Number Pin Name Pin Function 1 VINA Input voltage to control circuitry (2.9V to 14V). 2 SKIP Skip (Input): Regulator operates in PWM mode (no pulse skipping) when pin is pulled low, and skip mode when raised to VDD. There is no automatic switching between PWM and skip mode available on this device. 3 SS Soft Start (External Component) : Reduces the inrush current and delays and slows the output voltage rise time. A 5A current source will charge the capacitor up to VDD. 4 COMP Compensation (Output): Internal error amplier output. Connect to a capaci- tor or series RC network to compensate the regulators control loop. 5 SGND Small Signal Ground (Return) : Must be routed separately from other grounds to the () terminal of C . OUT 6 FB Feedback (Input) : Regulates FB to 1.245V. 7 EN/UVLO Enable/Undervoltaqe Lockout (Input): A low level on this pin will power down the device, reducing the quiescent current to under 0.5A. This pin has two separate thresholds, below 1.5V (typical) the output switching is disabled, and below 0.9V (typical) the device is forced into a complete micropower shutdown. The 1.5V threshold functions as an accurate undervoltage lockout (UVLO) with 140mV hysteresis. 8 VREF Voltage Reference (Output) : The 1.245V reference is available on this pin. A 0.1F capacitor should be connected form this pin to SGnd. 9 CSH Current Sense (Input) : The (+) input to the current limit comparator. A built in offset of 100mV (typical) between CSH and SGnd in conjunction with the current sense resistor sets the current limit threshold level. This is also the (+) input to the current amplier. 10 VDD 3V Internal Linear-Regulator (Output) : VDD is also the supply voltage bus for the chip. Bypass to SGND with 1F. Maximum source current is 0.5mA. 11 SYNC Frequency Synchronization (Input): Connect an external clock signal to synchronize the oscillator. Leading edge of signal above 1.4V (typical) starts switching cycle. Connect to SGND if not used. 12 PGND MOSFET Driver Power Ground (Return) : Connects bottom of current sense resistor and the () terminal of C . IN 13 OUTN N-Channel Drive (Output) : High current drive for n-channel MOSFET. Volt- age swing is from ground to V P. On-resistance is typically 5. IN 14 OUTP P-Channel Drive (Output) : High current drive for the synchronous p-channel MOSFET. Voltage swing is from ground to V P. On-resistance is typically IN 5. 15 FREQ/2 Frequency Divider (Input) : When this pin is low, the oscillator frequency is 400KHz. When this pin is raised to VDD, the oscillator frequency is 200KHz. 16 VINP Gate Drive Voltage (Input) : This is the power input to the gate drive cir- cuitry (2.9V to 14V). This pin is typically connected to the output voltage to enhance gate drive. MIC2185 2 October 2005