MIC2185_05 Datasheet, PDF (2/15 Pages) Micrel Semiconductor – Low Voltage Synchronous Boost PWM Control IC

MIC2185
Pin Configuration
Pin Description
Pin Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
MIC2185
VINA 1
SKIP 2
SS 3
COMP 4
SGND 5
FB 6
EN/UVLO 7
VREF 8
16 VINP
15 FREQ/2
14 OUTP
13 OUTN
12 PGND
11 SYNC
10 VDD
9 CSH
16-pin Narrow Body SOIC (M)
16-pin QSOP (QS)
Micrel, Inc.
Pin Name
VINA
SKIP
SS
COMP
SGND
FB
EN/UVLO
VREF
CSH
VDD
SYNC
PGND
OUTN
OUTP
FREQ/2
VINP
Pin Function
Input voltage to control circuitry (2.9V to 14V).
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.
Soft Start (External Component) : Reduces the inrush current and delays
and slows the output voltage rise time. A 5µA current source will charge the
capacitor up to VDD.
Compensation (Output): Internal error amplifier output. Connect to a capaci-
tor or series RC network to compensate the regulator’s control loop.
Small Signal Ground (Return) : Must be routed separately from other
grounds to the (–) terminal of C_OUT.
Feedback (Input) : Regulates FB to 1.245V.
Enable/Undervoltaqe Lockout (Input): A low level on this pin will power down
the device, reducing the quiescent current to under 0.5µA. 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.
Voltage Reference (Output) : The 1.245V reference is available on this pin.
A 0.1µF capacitor should be connected form this pin to SGnd.
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 amplifier.
3V Internal Linear-Regulator (Output) : VDD is also the supply voltage bus
for the chip. Bypass to SGND with 1µF. Maximum source current is 0.5mA.
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.
MOSFET Driver Power Ground (Return) : Connects bottom of current sense
resistor and the (–) terminal of C_IN.
N-Channel Drive (Output) : High current drive for n-channel MOSFET. Volt-
age swing is from ground to V_INP. On-resistance is typically 5Ω.
P-Channel Drive (Output) : High current drive for the synchronous p-channel
MOSFET. Voltage swing is from ground to V_INP. On-resistance is typically
5Ω.
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.
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.
2
October 2005